Veterinary Teaching Hospital, Equine Clinic and Large Animal HVAC Duct Guide

Why large animal veterinary HVAC is a different discipline

A community veterinary clinic conditions a 20 kilogram dog on an exam bench in a 16 square metre consult room. A large animal hospital conditions a 500 kilogram thoroughbred under anaesthesia on a hoist in a 140 cubic metre surgical bay, then recovers it in a padded box where the patient will stand within 45 minutes whether the room is ready or not. The two briefs share the words "veterinary" and "HVAC" and almost nothing else. The species is bigger by a factor of twenty-five, the room volumes are bigger by a factor of ten, the manure load is bigger by a factor of fifty, and the surgical anaesthetic gas inventory is bigger by a factor of three. The ventilation rates, the duct sizes, the diffuser face velocities and the material specifications all shift accordingly, and they shift in ways that the small-animal design literature does not address.

Our companion guides cover the adjacent disciplines: the community veterinary clinic and small animal hospital guide covers the suburban GP, 24-hour emergency and specialty referral clinic patient flow; the animal research and laboratory animal guide covers vivariums, PC2/PC3/PC4 biocontainment and the NHMRC code. This guide takes up the remaining brief — large animal clinical practice, teaching hospital infrastructure, equine racing-medicine, livestock handling and exotic animal hospital facilities. The audience is the mechanical consultant designing a university teaching hospital wing, the practice principal of a regional equine referral hospital, the racing-stable veterinarian setting up an on-site clinic at Randwick or Caulfield, the zoo veterinary works manager, and the duct fabricator quoting any of them.

Three engineering threads run through the entire guide. First, the air change rates in ASHRAE Applications Handbook Chapter 11 (animal facilities) are higher than the rates a small-animal designer would expect, and they are driven by manure ammonia, bedding dust and respiratory mucus output rather than by occupant CO₂. Second, the biosecurity envelope in any Australian equine clinic east of the Great Dividing Range and in any clinic north of the Tropic of Capricorn has to assume Hendra virus as the design pathogen, not as an occasional consideration. Third, the cleaning chemistry across the practice is aggressive — sodium hypochlorite at 5,000 ppm available chlorine, glutaraldehyde at 2 per cent, accelerated hydrogen peroxide at 7 per cent, citric-acid descaler on autoclave plumbing — and it eats galvanised duct in months. The default material specification is stainless across most of the practice, with galvanised only in supply ducts upstream of the room boundary.

This is the engineering reference SBKJ delivers when the next project is a University of Sydney Camden expansion, a Scone Equine Hospital surgical block, a Randwick Equine Centre fit-out, a Lort Smith ward refit, an Australia Zoo Wildlife Hospital extension or a Magic Millions sales-complex clinic. Every room type is covered with its air-change target, its setpoint, its pressure regime, its material specification and its acoustic limit, and the closing sections map the brief back to the SBKJ machine configuration that produces the ductwork.

Regulatory framework — the documents the engineer reads in parallel

Australian large animal veterinary HVAC sits at the intersection of more than a dozen documents. None of them is a single source of truth, and none of them addresses every room in the practice. The mechanical engineer who signs the certificate of compliance reconciles them at every room boundary.

• AS 1668.2 (Mechanical ventilation in buildings). Sets the minimum outdoor air rate for occupied rooms. Owner waiting rooms, reception, offices, classrooms and staff rooms are sized at 10 L/s per person plus 0.6 L/s per square metre of floor area. Stocks bays, ward stables, isolation barns and necropsy rooms are sized by air change rate and contaminant capture velocity from ASHRAE Applications rather than by the AS 1668.2 occupied-room formula, but the standard's dispersion and intake-separation rules govern every external exhaust termination.
• AS 4254 (Ductwork for air-handling systems). Construction standard for galvanised and stainless steel ductwork, seam types, sealant classes, support and bracing. Large animal veterinary fit-outs typically run seal class A construction for clinical extract and isolation barn ductwork, with seal class B acceptable on owner waiting and office areas.
• AS 1530.4 (Fire-resistance tests for elements of construction). Governs fire-rated duct construction at every penetration of a fire-rated wall. Critical at the boundary of the hay feed store, the cremation room (if on-site), the LPG plant room (some regional clinics) and the central sterilising department fire compartment.
• ASHRAE Applications Handbook Chapter 11 (Animal facilities). The international design reference for animal-facility ventilation. Air change rates for hospital ward stables, equine surgical stocks, isolation barns, necropsy rooms and equine MRI rooms come from Chapter 11 directly. The chapter covers species from laboratory rodent to large agricultural production animal, with explicit guidance on equine, bovine, ovine and small-ruminant programs.
• ASHRAE Standard 170 (Ventilation of healthcare facilities). Used as the analogue for the human-grade isolation rooms inside any university teaching hospital — the staff health room, the post-exposure decontamination shower and the bloodborne pathogen handling lab. Standard 170 is also the standard a designer cites when justifying the negative-pressure regime in the Hendra isolation barn under cross-referencing to Biosecurity Act controls.
• AS/NZS 4187 (Reprocessing of reusable medical devices). Applies to veterinary surgical instruments through the same workflow as human surgery: dirty-to-clean ventilation cascade through the central sterilising department, autoclave exhaust ducted separately to atmosphere, packing-room positive pressure and air-quality controls on the sterile storage area. Practices pursuing AVA Hospital of Excellence accreditation are audited against AS 4187.
• AS 2243 series (Safety in laboratories). The clinical pathology and histology lab inside the teaching hospital is governed by AS 2243.8 (fume cupboards), AS 2243.3 (microbiological aspects and containment), AS 2243.10 (storage and handling of dangerous goods) and AS/NZS 2982 (laboratory design and construction). The lab ventilation is independent of the clinical practice ventilation.
• AS/NZS 60079 series (Explosive atmospheres). Triggers where anaesthetic gas storage, oxygen storage or compressed gas plant generates a hazardous-area classification. Most modern halogenated anaesthetics (isoflurane, sevoflurane) are not classified as flammable at therapeutic concentrations, but the compressed-gas plant room may attract a Zone 2 classification, and an X-ray room with developer-and-fixer chemistry may attract a Zone 2 around the processor.
• AS 1940 (Storage and handling of flammable and combustible liquids). Applies to anaesthetic agent storage cabinets, alcohol-based hand rub bulk storage and the developer-fixer chemistry storage in older X-ray installations. The standard sets the cabinet ventilation rate and the maximum quantity stored in a workroom.
• AS 4180 / AS 4181 (Isolation procedures for zoonotic disease). Australian biosecurity guidelines on isolation procedure for zoonotic disease. The standards reference back to the Biosecurity Act 2015 and the state-level biosecurity legislation, and they cover the procedural side that the HVAC engineer's pressure cascade is built to support.
• AS 5588 (Biosecurity). National biosecurity standard cross-referenced to OIE WAHIS (World Organisation for Animal Health World Animal Health Information System) reporting. The HVAC implication is the design of the isolation barn for any reportable disease — equine influenza, anthrax, foot-and-mouth (notifiable suspect-handling only, never actual cases in Australia), Hendra virus.
• Biosecurity Act 2015 (Commonwealth). Triggers notifiable-disease handling protocols. Hendra virus is a Notifiable Animal Disease under the Act and a confirmed case requires reporting to the Commonwealth Department of Agriculture, Fisheries and Forestry (DAFF) and the relevant state Chief Veterinary Officer within 24 hours. The HVAC engineer's role is to provide the physical infrastructure that allows containment to be initiated when a suspect case arrives.
• Australian Veterinary Association (AVA) accreditation. The Hospital Accreditation Scheme audits practice infrastructure across three tiers: Standard, Hospital and Hospital of Excellence. University teaching hospitals, specialty equine referral practices, the larger 24-hour emergency practices and the major charity hospitals (Lort Smith) all target Hospital of Excellence; private equine clinics typically target Hospital tier; production animal practices (cattle and sheep) typically target Standard or Hospital depending on the surgical workload.
• Equine Veterinarians Australia (EVA) and Australia New Zealand College of Veterinary Scientists (ANZCVS). The professional bodies for equine and specialty practice. EVA guidelines on equine hospital infrastructure and ANZCVS specialist-college standards inform the room schedule for any practice operating at specialist-referral level.
• Safe Work Australia Workplace Exposure Standards. Set the time-weighted-average and short-term exposure standards for the chemicals in routine use across the practice: isoflurane 50 ppm (no formal STEL), nitrous oxide 25 ppm, formaldehyde 1 ppm STEL and 0.3 ppm TWA (necropsy and histology), ethylene oxide 1 ppm STEL (where used — most practices have moved away from EO sterilisation), ammonia 25 ppm STEL and 17 ppm TWA (animal urine and manure), respirable particulate 3 mg/m³ (bedding dust). Sevoflurane has no formal WES but most practices target below 2 ppm by analogy with the NIOSH halogenated-anaesthetic limit.
• AS 4326 (Wholesale and retail food premises). Triggers in any practice handling animal byproducts intended for downstream feed-grade rendering or in any clinic offering meat-condemnation services for the local DAFF inspector. Most practices route condemned material direct to incineration and AS 4326 does not apply, but the standard is read in any project with on-site rendering or animal-feed handling.
• Department of Agriculture, Fisheries and Forestry (DAFF), Australian Aquatic Veterinary Standards (AAVS), and the historical Australian Quarantine Inspection Service (AQIS). The Commonwealth controls govern import, export and quarantine-holding facilities. The HVAC implication is in any clinic operating an AQIS-approved quarantine box or supporting export-certification work.
• State Veterinary Practitioners Boards. Each Australian state licenses individual veterinarians and registers premises. State guidelines on radiation safety, Schedule 4 and Schedule 8 drug storage, anaesthetic safety and biosecurity vary in detail but converge on the same air-quality outcomes.
• National Construction Code (NCC) Volume One. Large veterinary specialty and teaching hospitals are Class 9a (health care) buildings under the NCC, attracting the more onerous mechanical ventilation, fire-engineering and accessibility provisions. Single-suite private clinics on agricultural land are typically Class 7b (storage) or Class 8 (laboratory) depending on the surgical workload. The classification is set by the consent authority and is worth confirming at the briefing stage.

None of these is optional. The mechanical engineer who certifies the air-balance report and the duct construction is the one who reconciles all of them across every room boundary.

Equine surgical stocks — the room everything pivots around

The equine surgical theatre is the largest single room in most large animal hospitals and the most demanding from an HVAC perspective. The room program: 10 to 14 metres long, 6 to 8 metres wide, 4.2 to 4.8 metres clear ceiling, fitted with overhead anaesthesia hoists, recumbent positioning hoists, surgical lights, a stainless surgical floor with central drainage and a separate scrub-up and instrument table set to one side. Room volume comes out at 90 to 140 cubic metres per surgical bay. Large referral hospitals run two parallel bays sharing a scrub-up; teaching hospitals run three to five bays.

The mechanical brief follows ASHRAE Applications Chapter 11 for the species and ASHRAE Standard 170 for the surgical-air-quality principles, with the practical adjustment that displacement ventilation suits the room geometry better than the mixing-flow patterns used in small-animal surgery. Air change rate is 6 to 10 ACH. Below 6 ACH the room cannot clear isoflurane and electrocautery smoke between cases; above 10 ACH the supply face velocity at the high-level diffuser bank becomes uncomfortable for the surgeon and chills the patient. At a 120 cubic metre room volume and 8 ACH, supply rate is 0.27 cubic metres per second, distributed across an 8 to 10 metre run of perforated linear diffuser along the longitudinal axis of the stocks.

Supply temperature is 18 to 22 degrees Celsius — colder than the rest of the practice — because the surgical team is gowned, gloved, capped and working under intense overhead lighting that adds 600 to 1,200 watts of radiant heat to the surgical field. The patient is on a heated mat to prevent intra-operative hypothermia, which is a real risk in a 500 kilogram horse under prolonged anaesthesia. Relative humidity is 45 to 55 per cent.

Supply distribution is the most important design decision in the equine theatre. The room is too large for a small-animal-style ceiling laminar-flow bank centered above the operating table — the table is 2.4 metres long and the room is 6 to 8 metres wide, so a centered laminar bank either covers only part of the patient or has to be impossibly large. The practical solution is a linear perforated diffuser running parallel to the long axis of the stocks at 3.6 to 4.2 metres above floor level, sized to deliver vertical downflow at 0.15 to 0.3 metres per second at the surgical field. Return is at low level on both long walls, drawing the contaminated air column down past the floor drainage and into the extract risers without re-entraining it through the surgical zone.

Pressure regime is plus 10 to plus 15 Pa relative to the corridor — lower than the small-animal surgery target of plus 15 Pa because the door openings are larger (equine theatre doors are 3.0 metres wide and 4.0 metres high to admit a horse on a recumbency cart) and the static pressure differential collapses faster on each door operation. The mechanical engineer compensates by oversizing the supply fan by 10 to 15 per cent over the static design rate to maintain the differential during typical door-cycle frequency.

Floor detailing matters. The surgical floor is sloped to a central or trench drain captured to the laundry-grade waste system, with stainless coaming around the drain to prevent splash erosion of any adjacent concrete. The drain is independent of the HVAC scope but interacts with it — the floor return duct is offset from the drainage line to prevent the return air being saturated with washdown moisture during between-case cleaning.

Anaesthetic gas scavenging is dedicated, separate from the room exhaust, ducted in 316L stainless from each anaesthetic machine through a moisture trap to a roof-mounted scavenging fan and atmospheric stack. The stack terminates at least 7.5 metres from any intake and 3 metres above the highest roof line. Spark-resistant brass-bronze trim is fitted on any rotating component in the scavenging path because halogenated anaesthetic vapours in the flammable concentration range are theoretically possible at the immediate machine outlet, even though the room-air concentration is well below the lower explosive limit.

Duct material in the equine theatre is 304 stainless on supply downstream of HEPA H13 filtration, and 316L stainless on extract because of intra-operative scrub-up chemistry (chlorhexidine, povidone-iodine, sodium hypochlorite between cases) and the heavy ammonia load if the patient defecates intra-operatively (common with sedated horses). The supply is externally insulated; the extract is bare 316L with externally clipped acoustic blanketing if NC verification at commissioning demands it. Internal acoustic lining is not acceptable in this service.

Acoustic target is NC 35. Surgical concentration matters and the diffuser whine at the high air change rate is the most common acoustic complaint at commissioning. Solved by oversizing the diffuser plenum, keeping face velocity below 2.0 metres per second and acoustically lining the supply branch upstream of the diffuser face but not the diffuser face itself.

Anaesthesia induction stocks and recovery box

The induction stocks is the room where the horse is sedated standing, then lowered to recumbency by the anaesthesia hoist and transferred to the surgical theatre. The room program: 5 to 7 metres long, 5 to 6 metres wide, 4.2 metres clear ceiling, padded walls and a padded floor, with an anaesthesia hoist and a recumbency cart that connects directly through to the surgical theatre.

The mechanical brief is 8 to 12 ACH because of manure odour and ammonia load from a conscious horse standing under sedation for 5 to 15 minutes before recumbency. Supply at high level above the door, return at low level on the far wall, supply temperature 20 to 22 degrees Celsius. Anaesthetic gas inventory is small in the induction stocks (the breathing circuit is connected only briefly), so anaesthetic gas scavenging is by face-mask scavenger ducted through 316L stainless to the central scavenging stack.

The anaesthesia recovery box is the most idiosyncratic room in the equine hospital. Patients exit anaesthesia in a padded recovery box where they will spend 20 to 60 minutes lying down, then attempt to stand — a process that involves repeated falling, scrambling and disoriented movement until full neuromuscular control returns. The room is 4 to 5 metres on a side with padded walls to 2.4 metre height, a padded floor, a single observation window from the recovery nurses' bay, and (in modern designs) an overhead camera and a remote-controlled door that allows staff to enter only when the horse is reliably standing. Air change rate is 8 to 10 ACH, supply at high level outside the recovery zone (no direct downflow on the disoriented patient), return at low level on the far wall.

Duct penetrations into the recovery box are detailed for patient safety — every supply diffuser, return grille, fire sprinkler head and lighting fixture is recessed flush with the padded surface or padded over to prevent injury during the standing attempts. The HVAC contractor coordinates with the padding specialist (typically a sports-flooring or equine-padding contractor) to ensure the duct face is set behind a single continuous padded surface that does not present a hard edge to the patient.

Acoustic target NC 35 — the recovering patient is sensitive to noise and a quiet recovery accelerates the return to stable hemodynamics. Diffuser whine on the high-level supply is the most common complaint; solved by oversized plenum and low face velocity.

Equine MRI and CT — climate-controlled imaging

Equine MRI installations in Australian referral hospitals are either standing low-field 0.27 to 0.4 Tesla systems imaging the lower limb of a sedated standing horse, or recumbent high-field 1.5 Tesla systems imaging the head, neck or limb of a fully anaesthetised recumbent horse on a gantry. The standing low-field system is the more common installation because it does not require general anaesthesia; the high-field system is found in university teaching hospitals (Werribee, Camden, Murdoch) and the largest private referral centres.

The MRI room program: 8 to 12 metres long, 6 to 8 metres wide, 3.6 to 4.2 metres ceiling (low-field standing) or 4.2 to 4.8 metres ceiling (high-field recumbent to admit the gantry hoist), inside a Faraday cage of copper or galvanised sheet laminated into the wall and ceiling construction. The Faraday cage excludes radio-frequency interference from the gradient and receive coils — RF interference is the dominant artefact source in MRI imaging and the Faraday cage is the only effective control.

Room conditioning is 22 to 24 degrees Celsius and 45 to 55 per cent relative humidity. The temperature setpoint is tighter than elsewhere in the practice because the gradient coil drift with temperature affects image geometry, and the cryogen recovery system for the superconducting magnet operates within a narrower band when the room is stable. Air change rate is 6 to 8 ACH — the room is not heavily occupied during scans and the dominant thermal load is the magnet itself, which dissipates 5 to 12 kilowatts continuously plus 30 to 60 kilowatts transient during a scan from the gradient amplifiers.

HVAC penetration of the Faraday cage is the design problem. Direct penetration breaks the RF containment. The two acceptable solutions are a waveguide (a length of conductive duct that is much longer than its diameter, attenuating RF by mode-cutoff) or a fully copper-mesh-lined duct boot with a 360-degree grounded contact between the duct and the cage. Waveguides are sized at the inverse-cube-root of the operating frequency — for a 1.5 Tesla system operating at 63.8 MHz, the cutoff diameter is approximately 88 millimetres for a circular waveguide and the duct must be at least 4 diameters long, so a 200 millimetre waveguide that is 800 millimetres long is the practical minimum. Copper-mesh-lined boots are used where the duct diameter would force an impractically long waveguide.

The magnet quench vent is separate from the HVAC. The quench vent is the emergency vent that releases helium gas if the superconducting magnet quenches (loses superconductivity, dumping 200 to 600 litres of liquid helium as gas in 30 seconds). The vent is sized by the magnet manufacturer for the helium discharge volume — typically 200 to 400 millimetres diameter — and terminates direct to atmosphere outside the building. The vent is fail-safe open, has no damper, and is never used for ventilation purposes.

Equine CT installations are conditioned similarly at 6 ACH with the cooling load dominated by the X-ray tube heat exchanger. A typical equine CT (large-bore 80 to 90 centimetre gantry, designed to admit a recumbent horse limb or a small ruminant whole-body) dissipates 12 to 18 kilowatts continuously during operation. The scan room is on a dedicated air conditioning circuit sized for the load. Lead-shielded wall construction is detailed by the radiation safety consultant; HVAC penetrations through the shielded wall are leaded-sleeve detail with the radiation physicist signing off the as-built.

Duct material in MRI and CT is galvanised on supply (room air is not biologically contaminated and the cleaning regime is benign) and 304 stainless on extract only where the room handles a sedated patient that may defecate (relevant to the recumbent MRI suite). Acoustic target NC 40 — the scanner noise floor is dominant during a scan and a tighter HVAC target is not perceptible to staff.

Equine wash bay — humid extract and 316L stainless

The wash bay is where the horse is washed before surgery, between training sessions, after hot-walker work and at the end of every routine veterinary procedure. The room program: 4 to 6 metres long, 4 to 5 metres wide, 3.0 to 3.6 metres ceiling, with a slip-resistant rubber-matted floor sloping to a central drainage gully captured to the wash-water waste system. The horse is tied to a wall point or held by a handler during the wash.

The wash bay operates at near 100 per cent relative humidity during the active wash phase, which lasts 5 to 15 minutes. Water temperatures range from cool ambient for routine rinsing to 35 to 38 degrees Celsius for therapeutic post-exercise washing. The chemistry includes mild shampoo, sodium hypochlorite at 100 to 500 ppm available chlorine for biosecurity rinses and the occasional therapeutic chlorhexidine wash for skin conditions.

The HVAC brief is 10 to 15 ACH dedicated extract, with supply tempered at 22 to 24 degrees Celsius. The extract grille is at low level along the long walls of the wash bay to capture the rising humid air column and the bedding-dust laden return from the horse's coat; supply is at high level outside the wet zone to deliver fresh air without driving droplets into the ceiling void. Extract face velocity is 4 to 6 metres per second to maintain capture of the humid air column at the source.

Ductwork material is 316L stainless from the grille face back at least 5 metres to the first riser, externally insulated to prevent ceiling-void condensation. Galvanised fails in this service inside 12 to 18 months — the zinc coating dissolves under continuous exposure to high-humidity chlorinated air. 304 stainless develops chloride pitting where the hypochlorite concentration spikes during a biosecurity rinse. 316L stainless, with its molybdenum content, resists chloride pitting at the concentrations encountered in routine wash bay service.

The longitudinal seam on the extract duct is welded — Pittsburgh seam construction is acceptable but the seam is the highest-leak path in a humid extract and welded seam is the conservative specification for the 25-year design life expected of a major teaching hospital. The SBKJ Stitch Welder (model SBSW-30-2Z) welds 0.4 to 1.0 millimetre stainless sheet at 2 metres per minute and is the standard equipment for this service.

Acoustic target NC 40. The wash bay is intrinsically noisy with water spray and grooming activity, and a quieter HVAC target is not perceptible.

Hot-walker and treadmill rooms — sweat, manure and forced cooling

Equine hot-walker and treadmill rooms support sweating horses at moderate to high exercise intensity, either as part of rehabilitation programmes (most metropolitan equine clinics) or as a training-aid facility (Living Legends Greenvale VIC, the larger thoroughbred training stables). The room program: 8 to 12 metres long, 6 to 8 metres wide, 3.6 to 4.2 metres ceiling, with a circular hot-walker track or an inline horse treadmill, drainage to handle sweat and urine, and CCTV monitoring from the trainer's station.

The HVAC brief is 8 to 10 ACH with cooling capacity sized for the sensible heat load of a working horse — typically 1.5 to 2.5 kilowatts per horse at moderate exercise plus the latent load of sweat evaporation (a horse at gallop produces 10 to 15 litres of sweat per hour, which represents 7 to 10 kilowatts of latent cooling that must be replaced by the air conditioning system). The room conditioning is therefore dominated by latent rather than sensible load, and the air conditioning system is sized for the dew-point control rather than for the dry-bulb temperature.

Supply is at high level around the perimeter of the room, return at low level near the walking track to capture the rising humid air column from the working horse. Supply temperature is 18 to 20 degrees Celsius (low for an Australian climate to provide latent cooling capacity). Relative humidity target is 50 to 70 per cent — higher than elsewhere in the practice because the horse is generating moisture rapidly and a low-humidity setpoint is not achievable without disproportionate fan power.

Ductwork material is 304 stainless on extract because of manure odour, sweat aerosol and bedding dust load. Supply is externally-insulated galvanised. The acoustic target is NC 45 — the treadmill or hot-walker is the dominant noise source and a quieter HVAC target is not relevant.

Hospital ward stables — individually-conditioned stalls

The hospital ward stable block is where the patient horse spends most of its hospitalisation time. The block consists of 6 to 16 individually-monitored stalls (12 is the typical specification in modern Australian referral hospitals), each 3.6 by 3.6 metres or 4.0 by 4.0 metres, with a 3.0 to 3.6 metre ceiling, equipped with a heated water bucket, an automatic or manually-filled feeder, rubber matting over concrete with bedding on top, and CCTV with a feed to the nurses' station.

The HVAC brief follows ASHRAE Applications Chapter 11 recommendations for an individually-stalled hospital horse: 8 to 12 ACH per stall, 100 per cent outside air on the exhaust side, never any recirculation between stalls. Supply is at high level above the stall door at a face velocity of no more than 0.3 metres per second at muzzle level to prevent draft on a wet or post-operative patient. Return is at low level on the back wall of each stall to capture ammonia from urine, manure odour and respirable bedding dust.

The critical design rule is that each stall has its own supply branch and its own return branch. Shared trunks between stalls are not acceptable because of cross-contamination of equine respiratory pathogens through shared ductwork: Streptococcus equi subspecies equi (strangles), equine herpesvirus 1 and 4, equine rhinitis virus, equine influenza, Rhodococcus equi (in foals) and rotavirus. The trunk ducts cross-link stalls but the return collector serves only one stall at the diffuser, with each branch capable of being isolated by a damper at the trunk side when a stall is occupied by a suspect-case patient.

Supply temperature is 18 to 22 degrees Celsius in cooler months and 20 to 24 degrees Celsius in warmer months. Most Australian metropolitan equine hospitals run year-round air conditioning on the ward block because the patient population includes recently-clipped racing thoroughbreds that have lost their winter coat for the season and convalescent horses that have lost body condition through illness.

Ductwork material is 304 stainless on extract because of ammonia, manure odour and the chlorhexidine-based stall disinfection routine used between patients. Supply is externally-insulated galvanised. The acoustic target is NC 40 — horses are sensitive to noise and a calm ward accelerates clinical recovery.

Equine isolation barn — Hendra virus and the negative-pressure envelope

The isolation barn is the most engineering-critical room in any Australian equine clinic operating east of the Great Dividing Range and any clinic operating north of the Tropic of Capricorn. The design pathogen is Hendra virus, a paramyxovirus carried by flying foxes (Pteropus species) and known to spill over into horses through contamination of feed and water with bat urine, faeces or birthing fluids. Hendra virus is a Notifiable Animal Disease under the Biosecurity Act 2015 and a Notifiable Human Disease under state Public Health Acts. Confirmed human cases have a case-fatality rate above 50 per cent (the published count is 4 deaths in 7 confirmed cases over the period 1994 to 2023).

Hendra spillover events have been confirmed in Queensland and northern New South Wales since the first 1994 Brisbane outbreak. Flying fox range has shifted southward over the last two decades and coastal Victoria has documented flying fox roosts in the Melbourne region since the 2010s. The HVAC engineer designing any equine clinic east of the Great Dividing Range now treats the isolation barn as a default infrastructure requirement, not as an optional extra.

The isolation barn program: 1 to 4 stalls (typically 2) at 4.0 by 4.0 metres each, 3.0 to 3.6 metre ceiling, plus a PPE lobby of 6 to 10 square metres at the entry, plus a separate carcass exit lobby of similar size. The barn is accessed from an external one-way race that is not shared with the main hospital flow, so a suspect-case animal can be stocked from the float park direct to the isolation barn without passing through the main hospital reception or ward block.

The HVAC brief is the most rigorous in the practice. Air change rate is 12 to 15 ACH with single-pass ventilation — never any recirculation, under any condition. Pressure regime is minus 15 Pa relative to the corridor, verified at commissioning with a digital manometer and again at quarterly intervals. The PPE lobby is at plus 5 Pa relative to the isolation barn, which means the staff entering the barn through the PPE lobby breathe clean supply air during gowning, with the air-flow direction always from the clean PPE lobby into the contaminated barn.

Exhaust is HEPA H13 filtered before atmospheric discharge. The HEPA filter is housed in a bag-in-bag-out housing with leak-test ports for in-situ DOP (dioctyl phthalate) or PAO (poly-alpha-olefin) challenge testing, sized for the design flow rate plus a 25 per cent margin to accommodate filter loading over the service life. The housing is a welded 316L stainless fabrication, supplied either by a specialist HEPA housing manufacturer or fabricated on-site by a duct contractor using a TIG-capable stitch welder such as the SBKJ SBSW-30-2Z.

The exhaust stack terminates at least 7.5 metres from any building intake and 3 metres above the highest roof line per AS 1668.2 dispersion principles. In a Hendra-endemic catchment (Queensland coast, Hunter Valley) the stack is fitted with a charcoal scrubber upstream of the discharge — a fixed-bed activated carbon filter providing additional capture of any aerosolised pathogen that bypasses the HEPA. The charcoal is regenerated or replaced annually and the spent media is disposed through clinical waste rather than general waste.

The PPE lobby supply is from a dedicated air handling unit with HEPA H13 supply filtration, sized to maintain the plus 5 Pa positive pressure differential at design infiltration rates. The lobby is detailed with a one-way inward door from the corridor and a one-way outward door to the isolation barn, with the doors interlocked so that only one door is open at a time. The lobby supplies the gowning area with clean air during the donning and doffing routine.

Ductwork material is 316L stainless throughout the isolation barn envelope. Cleaning chemistry is sodium hypochlorite at 1,000 to 5,000 ppm available chlorine — too aggressive for 304 stainless over the design life, and definitively too aggressive for galvanised. Seam construction is fully welded longitudinal and circumferential on every duct section, with pressure-decay leak testing at commissioning to confirm leak rate below 0.05 per cent of system volume. The SBKJ SBAL-V with TIG welding station configuration is the standard line for this fabrication.

Decontamination cycles use vaporised hydrogen peroxide (VHP) or chlorine dioxide gas through the duct system before any duct opening or HEPA filter change. The duct material and gasket selection is verified compatible with both decontamination agents at commissioning, and the cycle parameters (concentration, contact time, relative humidity) are recorded against challenge-organism kill verification per AS/NZS 2243.3:2022.

Acoustic target NC 45 — the barn is intentionally a calm environment for the suspect-case patient and the engineering noise floor is dominated by the high-rate extract fans which are typically located on the roof and silenced into the barn through a duct silencer upstream of the room boundary.

Cattle and sheep handling crush — agricultural-grade ventilation

Multi-species large animal practices handle production animals (cattle, sheep, goats, alpaca, deer) through a handling crush room. The room is a covered yard rather than a fully-enclosed clinical space, with a hydraulic crush at the working position, scales and processing race, lead-up forcing yard and exit gate. The crush room is a clinical-procedure space rather than a hospitalisation space — animals enter for examination, vaccination, pregnancy testing, surgery (caesarean section, eye surgery), reproduction work or condition scoring, and exit within minutes to hours rather than remaining for overnight care.

The HVAC brief is 6 to 8 ACH agricultural-grade ventilation. Where the crush is in a fully-enclosed shed (university teaching hospital, regional referral practice), mechanical ventilation delivers the air change rate with bird-mesh screened intakes and high-level exhaust fans. Where the crush is in a covered open-sided yard (most regional and on-farm practice), natural ventilation through the open sides is the primary mechanism with mechanical extract reserved for odour-management at any indoor pharmacy or surgical bay attached.

Respirable particulate target is below 3 mg/m³ per Safe Work Australia. Cattle handling generates significant respirable dust from dried manure on the hide and from any straw or sawdust bedding in the lead-up race, and the work is sustained over hours rather than minutes during a large processing run (a station vet processing 200 to 400 cattle per day at calf-marking).

Ammonia load is high but typically managed by frequent washdown rather than by ventilation. The room is hosed down at the end of each working day and the manure and urine are flushed to a holding lagoon outside the building envelope. Where the room is used continuously through the working week without daily washdown, the ammonia target is below 25 ppm short-term per Safe Work Australia, achieved by 8 to 10 ACH and low-level extract at the manure-load points.

Ductwork material is stainless-coated steel where ammonia is controlled by frequent washdown, 304 stainless where the room is used continuously. Galvanised is acceptable in supply only. The economic decision favours stainless from the grille face back to the first riser for any room with ammonia exposure above 10 ppm at sustained levels, because the zinc coating fails in 24 to 36 months in this service and the labour cost of replacement exceeds the material premium of stainless in the original build.

Acoustic target is NC 50 or higher — the room is intrinsically noisy with hydraulic crushes, cattle vocalisation and processing-equipment noise, and a quieter HVAC target is not perceptible.

Necropsy and post-mortem — formaldehyde, downdraft and HEPA exhaust

The large animal necropsy room is the workhorse of the teaching hospital pathology service and a critical resource for the regional referral practice handling disease investigation, insurance post-mortems and forensic veterinary cases. The room program: 12 to 20 metres long, 8 to 10 metres wide, 4.2 to 4.8 metre ceiling, with 2 to 4 work bays each fitted with a downdraft post-mortem table and an overhead crane rated to lift a 1,000 kilogram carcass.

The HVAC brief is the most aggressive in the practice on extract terms. Air change rate is 12 to 20 ACH at 100 per cent outside air, with no recirculation under any condition. Pressure regime is minus 30 Pa relative to the corridor — the lowest in the building — to contain odour, aerosol and any aerosolised biological agent within the room. Exhaust is dedicated to atmosphere through HEPA H13 and activated carbon, sized for the design flow rate plus 25 per cent margin.

Supply is from a perforated ceiling diffuser bank covering the work zone, arrayed to deliver vertical downflow at 0.15 to 0.25 metres per second to support the downdraft table capture velocity without disturbing it. Supply temperature is 18 to 21 degrees Celsius for staff comfort under impervious gowns and aprons during sustained post-mortem work. Relative humidity is 45 to 55 per cent.

The downdraft post-mortem table is the local control measure for formaldehyde, aerosol and odour. Each table draws air through the work surface at 0.5 to 0.7 metres per second face velocity and discharges to a dedicated table-extract riser captured back to the room exhaust through HEPA. The table extract is independent of the room extract in flow terms but the two streams converge at the HEPA bank to share the filtration train.

Formaldehyde control is the dominant chemistry challenge. Carcass tissue fixation for histopathology uses 10 per cent neutral buffered formalin (3.7 per cent formaldehyde) in containers held within the downdraft table envelope during sampling. The Safe Work Australia workplace exposure standard for formaldehyde is 1 ppm short-term exposure limit and 0.3 ppm time-weighted average over an 8-hour shift; teaching hospital pathology services typically target a tighter internal limit of 0.5 ppm TWA. The annual exposure measurement programme uses passive samplers worn by pathology staff or a continuous photoacoustic monitor at the work zone.

Sodium hypochlorite cleaning between cases is at 5,000 to 10,000 ppm available chlorine — aggressive chemistry that drives the material specification to 316L stainless throughout the necropsy envelope. Ductwork is fully welded on longitudinal and circumferential seams to prevent corrosion-induced pinholing at the seam line over the design life.

Acoustic target is NC 45. The work is intrinsically noisy with bone saws, oscillating saws, high-pressure water spray and overhead crane operation, and a quieter HVAC target is not achievable without compromising the airflow needed for the air change rate.

Clinical pathology, histology and microbiology lab

The clinical pathology lab in a large animal teaching hospital is a substantial space — typically 80 to 200 square metres at the major university teaching hospitals — running haematology, biochemistry, urinalysis, parasitology, cytology, histology, microbiology culture and antimicrobial susceptibility testing. The histology section handles fixed tissue from necropsy and from biopsy referral, and the microbiology section handles cultures up to AS/NZS 2243.3:2022 Physical Containment Level 2 (PC2) routinely, with PC3 capability for selected reference work at the larger universities (UQ Gatton, Sydney Camden, Melbourne Werribee).

The mechanical brief follows AS/NZS 2982 (laboratory design and construction) and AS 2243.8 (fume cupboards) for the chemical chemistry side, and AS/NZS 2243.3:2022 for the microbiological containment side. Air change rate is 10 to 12 ACH at 100 per cent outside air, neutral to slightly negative pressure relative to the corridor (minus 5 Pa) to prevent migration of chemical and biological aerosols into the adjacent practice areas.

Fume cupboard provision is sized at one cupboard per 4 to 6 bench positions for histology (xylene, ethanol, formaldehyde) and one cupboard per 8 to 10 bench positions for general chemistry. Each fume cupboard is ducted independently to atmosphere through 316L stainless ductwork with face velocity verified at commissioning at 0.5 metres per second with the sash at 500 mm opening. Cupboard exhaust is never recirculated and never combined with the room exhaust.

Biological safety cabinet provision is one Class II BSC per microbiology bench position, ducted to atmosphere through HEPA H14 with a bag-in-bag-out housing for safe filter change. PC2 work uses Class II Type A2 cabinets recirculating internally with HEPA on supply and exhaust; PC3 work uses Class II Type B2 cabinets hard-ducted to atmosphere through HEPA.

Ductwork material is 304 stainless on fume cupboard and BSC exhaust through the lab envelope, transitioning to 316L stainless where the exhaust handles formaldehyde or chlorinated chemistry over the long-term service life. Acoustic target NC 40 — laboratory work involves concentration but the bench-and-cupboard noise floor sets the practical limit.

Imaging suite — X-ray, ultrasound, CT and MRI in the teaching hospital

The imaging suite in a large animal teaching hospital handles the full diagnostic imaging chain. Most modalities have been covered in dedicated sections (CT and MRI under equine imaging above), but the suite as a whole has shared characteristics that the design engineer addresses at the planning stage.

General radiography for large animals uses ceiling-mounted X-ray tubes on overhead suspension rails serving 2 to 4 positioning bays, with the patient positioned for limb, thoracic or abdominal images. Each bay has lead-shielded walls and a leaded-glass control viewport. HVAC follows general treatment ventilation at 8 to 10 ACH, neutral pressure, 22 degrees Celsius, NC 40 acoustic. Lead-shielded penetrations through the walls are leaded-sleeve detail with the radiation physicist signing off the as-built.

Equine ultrasound rooms (general abdominal, reproductive ultrasonography, cardiac ultrasonography) are general-purpose clinical-equivalent rooms at 6 to 8 ACH, 22 to 23 degrees Celsius, low ambient lighting at 50 to 200 lux at the bench. Acoustic NC 35 to support clear communication during scan acquisition. Ductwork galvanised on supply, 304 stainless on extract because of ultrasound coupling-gel residue and routine wipe-down disinfection.

Dental radiography for horses uses a wall-mounted portable X-ray source positioned at the head of a standing sedated patient, with the dental film cassette inserted intra-orally. The room is a sub-bay of the dental stocks rather than a separate room in most facilities, with the radiation shielding extending to the dental stocks walls. HVAC follows the dental stocks brief at 10 to 12 ACH for ammonia and aerosol capture.

Nuclear medicine capability exists at three Australian universities (Sydney Camden, Melbourne Werribee, UQ Gatton) for equine bone scintigraphy. The room is a radiation-controlled area with shielded walls, dedicated ventilation discharging to atmosphere through HEPA filtration, and a separate exhaust stack on the radioactive-waste discharge envelope. The scope is specialised and the design is led by the radiation safety consultant; the HVAC engineer details the room ventilation and the exhaust train.

Cleanroom-grade orthopaedic suite — ISO 7 for the highest-risk surgery

Equine orthopaedic surgery (arthroscopy, fracture repair with bone plates, joint replacement, limb-sparing osteosarcoma surgery in small ruminants and exotic mammals) is the highest infection-risk procedure in the large animal practice. The intra-operative bacterial contamination drives prosthetic joint infection rates that are clinically catastrophic in a 500 kilogram horse with an implanted hip plate or arthrodesis screw — the surgical revision rate is high, the clinical morbidity is severe, and the patient outcome at re-operation is poor.

The mechanical brief is therefore upgraded from the general surgical specification to ISO 7 cleanroom classification per ISO 14644 (less than 352,000 particles per cubic metre at 0.5 micron MPPS when occupied). Supply filtration is HEPA H14 (greater than 99.995 per cent at MPPS) with a laminar-flow diffuser bank directly above the surgical field, sized to deliver a 0.3 to 0.5 metres per second vertical air curtain across the surgical wound. Air change rate is 15 to 20 ACH — the upper end of the surgical range — and the pressure differential to the corridor is plus 20 Pa.

Supply distribution is the most demanding design problem in the orthopaedic suite. The laminar-flow bank covers the surgical field with vertical downflow and isolates the field from room air recirculation. The bank is sized at 3.0 by 3.6 metres minimum to cover the equine patient on the table plus the surgical team's working envelope. Return is at low level on the opposite walls, drawing the contaminated air column down past the floor without re-entrainment.

Surgical staff are gowned in disposable single-use suits with internal exhaust connected to a separate body-exhaust vacuum line, drawing exhaled breath and shed skin scale away from the surgical zone. The body-exhaust vacuum is ducted in 316L stainless to atmosphere through HEPA, and is separate from the room exhaust.

Anaesthetic gas scavenging is dedicated through 316L stainless with spark-resistant brass-bronze trim on rotating components in the scavenging path. The anaesthetic agent inventory in an orthopaedic procedure is high because the procedure is long (often 4 to 8 hours), and the scavenging system must maintain capture efficiency over the duration without breakthrough.

Acoustic target is NC 30 — the surgeon is operating at fine-motor scale through magnification loupes or a microscope, and noise fatigue compromises outcomes. The diffuser whine at the high air change rate is the most common acoustic complaint at commissioning; solved by oversized plenum, low face velocity and acoustic lining on the supply branch upstream of the diffuser face.

Ductwork material is 304 stainless on supply downstream of HEPA H14 (HEPA-protected, low contamination risk on the duct interior), and 316L stainless on extract because of intra-operative hypochlorite cleaning chemistry. Full-welded longitudinal seams on the extract.

Central sterilising department — AS/NZS 4187 in the large animal context

The central sterilising department in a large animal teaching hospital is a substantial facility serving the orthopaedic, soft-tissue, ophthalmic and dental surgical workload across the hospital. The CSSD program: 80 to 200 square metres, with separate dirty-receive, manual-clean, ultrasonic and washer-disinfector area, inspect-and-pack area, autoclave bay, sterile storage and dispatch.

The mechanical brief follows AS/NZS 4187 (Reprocessing of reusable medical devices) — written for human-health settings but accepted as the benchmark for veterinary reprocessing in any practice pursuing AVA Hospital of Excellence accreditation. The pressure cascade runs from dirty-receive at minus 15 Pa, through manual clean at minus 10 Pa, to inspect-and-pack at plus 10 Pa (relative to dirty), to autoclave bay at neutral, to sterile storage at plus 15 Pa (relative to packing).

Air change rates are 10 ACH on the dirty side and 8 ACH on the clean side, with 100 per cent outside air on the dirty exhaust and recirculation acceptable on the clean side downstream of HEPA H13 supply filtration. The clean side is conditioned at 21 to 22 degrees Celsius and 30 to 60 per cent relative humidity to maintain sterile barrier integrity on packaged instruments.

The autoclave bay handles steam steriliser discharge to atmosphere through a dedicated steam vent with a condensate trap on the discharge line. The vent is 316L stainless because of saturated steam chemistry and the trace chloride content of municipal water. Room ventilation in the autoclave bay is 10 ACH to manage the radiant heat load from the steriliser jacket and the latent moisture load from the steam discharge.

Ductwork material is 316L stainless on dirty-side exhaust and on the autoclave steam vent because of detergent and ultrasonic cleaning chemistry, glutaraldehyde or accelerated hydrogen peroxide between-batch disinfection, and steam-vent chemistry. The clean side runs 304 stainless on extract and externally-insulated galvanised on supply.

Acoustic target NC 35 on the clean side (concentration on packing accuracy), NC 40 on the dirty side (the work is noisy and the target is the practical limit).

Pharmacy, compounding and controlled drug storage

The pharmacy in a large animal teaching hospital is a substantial space dispensing across two channels: bulk dispensing to the hospital ward stables (where the patient drug regime is recorded against the cage number) and over-the-counter dispensing to client owners visiting the practice in the case of regional and equine referral hospitals. The pharmacy program: 30 to 80 square metres with a dispensing bench, a controlled-drug cabinet, a vaccine refrigeration cabinet, a compounding bench and a stock-pick area.

Ambient HVAC is 22 to 24 degrees Celsius, 6 ACH, neutral pressure. Most veterinary medicines have a 15 to 25 degrees Celsius storage range and stability data is invalidated by excursions outside that range. Vaccine refrigeration is by dedicated medical refrigerator on a monitored alarm circuit; the HVAC system is sized to keep the surrounding room temperature stable so the refrigerator compressor cycle is predictable.

Compounding bench (where individual prescriptions are made up from bulk medicines or where chemotherapy agents are prepared) uses a Class II biological safety cabinet for cytotoxic preparation and a general-purpose chemical fume hood for non-cytotoxic compounding. Both are vented to atmosphere through HEPA and activated carbon, never recirculated to the room. The compounding room is at negative pressure of minus 10 Pa relative to the corridor to contain any aerosolised compound to the room.

Schedule 8 controlled drug storage (ketamine, methadone, buprenorphine, fentanyl, morphine, midazolam) is in a tamper-proof cabinet with audit-logged access in a separately ventilated bunded room. The cabinet ventilation is sized at 4 to 6 ACH to manage any vapour leakage and to provide a draft-free environment for the audit log printer.

Ductwork material is 316L stainless on compounding-bench extract because of cytotoxic and citric-acid compounds, and 304 stainless on general pharmacy extract. Supply is externally-insulated galvanised. Acoustic target NC 35.

Reception, owner waiting and laneway zones

Reception and owner waiting in a large animal practice has a different geometry from a small-animal clinic. Owners typically arrive with a float and a horse, deliver the horse to the laneway entrance and wait in a covered awning rather than an indoor lobby. Metropolitan referral hospitals (Werribee, Camden, Murdoch) have a more formal indoor owner waiting area at 80 to 200 square metres, with the awning maintained as a secondary outdoor waiting zone for the float load-up.

The indoor owner waiting room is conditioned to AS 1668.2 minimums of 10 L/s per person plus 0.6 L/s per square metre of floor area, with 6 ACH and an acoustic target of NC 40 — owners often arrive distressed with critical-case animals and a calm waiting environment matters. Temperature setpoint is 22 to 23 degrees Celsius, relative humidity 50 per cent.

The covered laneway awning is a partially-enclosed structure with natural ventilation through the open sides. Where the awning attaches to the building envelope (typical of every modern equine clinic), the HVAC system is designed to maintain a slight positive pressure in the indoor zones relative to the awning to prevent migration of laneway dust and manure odour into the indoor zones during door opening.

Ductwork material is galvanised throughout the owner waiting and laneway area — there is no clinical contamination risk that mandates stainless, and the cleaning regime is standard janitorial. Acoustic NC 40 throughout.

Tack room, feed and hay storage

The tack room stores saddles, bridles, halters and grooming equipment for the resident patient and visiting horses. The room is climate-controlled at 18 to 24 degrees Celsius and 45 to 55 per cent relative humidity to preserve leather and prevent rope and webbing degradation. Air change rate is 4 to 6 ACH, neutral pressure, NC 40 acoustic. Ductwork galvanised throughout.

Hay feed stores require minimal-dust positive ventilation at 4 to 6 ACH with combustion-resistant construction (hay is a documented fire load — round-bale and square-bale hay stored at ambient conditions has a documented spontaneous combustion risk at moisture contents above 22 per cent), AS 1530.4 fire-rated penetrations through any boundary wall, and bird-mesh screened intakes to prevent bird and rodent access. Ductwork is galvanised; the fire-rated penetration sleeve is the critical detail.

The grain store and concentrate feed area is a sub-zone of the feed storage with the same brief at lower dust load. Where a feed mixer or rolled-grain operation is on-site, dust extraction is sized for the respirable particulate target below 3 mg/m³ per Safe Work Australia.

Vet ambulance bay and float park

The vet ambulance bay houses the practice's mobile vet vehicle (typically a fitted-out 4WD or twin-cab utility) and the float park accommodates client floats during patient delivery and discharge. The bay is open-sided to the laneway in most installations, with mechanical extract at the rear wall to capture diesel exhaust during engine warm-up and the brief idle on departure.

Diesel exhaust extract is sized at 8 to 10 ACH with a low-level capture grille at vehicle exhaust pipe height. Where the bay is fully enclosed (rare in equine practice), the extract is engineered for the residual carbon monoxide level below 25 ppm short-term and 17 ppm time-weighted average per Safe Work Australia. Ductwork material is galvanised; the cleaning regime is standard janitorial.

On-site cremation and mortuary

On-site cremation is offered by a minority of large animal practices, typically the larger equine clinics with a substantial racing-thoroughbred clientele where rapid disposal of a deceased patient is a service expectation. The cremation room is a dedicated space with a high-temperature incinerator (typically 850 to 1,100 degrees Celsius primary chamber, 1,100 to 1,200 degrees Celsius secondary chamber for hydrocarbon afterburn) and a stack abatement train.

The cremation room HVAC is independent of the practice HVAC scope — the incinerator and its abatement train are governed by EPA jurisdictional licensing in each Australian state and the design is led by an environmental engineering consultant rather than the practice mechanical engineer. The practice HVAC engineer details only the room ventilation (8 to 10 ACH for radiant-heat removal from the incinerator jacket, with supply tempered to compensate for the radiant heat gain) and the boundary detail at the room envelope.

Mortuary storage (short-term refrigerated holding of carcasses awaiting incinerator or off-site cremation) is at 4 degrees Celsius in a walk-in cold room with dedicated extract at 10 ACH ducted to atmosphere separate from the general HVAC. Ductwork is 316L stainless because of decomposition acidic chemistry and routine sodium hypochlorite cleaning.

Anaesthetic gas scavenging — design detail for the large animal practice

Anaesthetic gas scavenging in a large animal practice handles substantially more gas than a small-animal equivalent. A surgical procedure on a 500 kilogram horse uses 8 to 12 litres per minute of fresh gas flow at induction and 4 to 8 litres per minute at maintenance — three to five times the flow rate of a small-animal anaesthetic, sustained over 1 to 8 hours per case. The scavenging system handles 50 to 100 litres per minute of waste gas per active anaesthetic station, and a teaching hospital with 4 to 6 simultaneous theatres aggregates 200 to 600 litres per minute at peak.

The system has four elements. The interface is an active-scavenging interface valve at each anaesthetic machine, connected to the machine's adjustable pressure-limiting valve outlet and presenting a calibrated low-pressure regulator to the room. The transfer hose is a 30 millimetre conductive corrugated hose from the interface to the room wall. The scavenging duct is 316L stainless, sloped at 1:200 toward a moisture trap, sized for the connected anaesthetic machine population at 75 to 100 L/min nominal flow per machine. The active extract fan is a roof-mounted dedicated fan sized for the aggregate flow plus 25 per cent margin, providing the negative pressure that pulls waste gas from each interface to atmosphere.

Spark-resistant brass-bronze trim is fitted on every rotating component in the scavenging path. Halogenated anaesthetic vapours (isoflurane, sevoflurane, desflurane) are not classified as flammable at the room-air concentrations encountered in normal practice, but the concentrations at the immediate machine outlet during high-flow induction can transiently enter the flammable range. The spark-resistant specification is a defensive engineering choice rather than a code requirement, and is the standard in every major Australian teaching hospital.

Termination is at atmosphere at least 7.5 metres from any building intake and 3 metres above the roof line per AS 1668.2 dispersion principles. The termination is fitted with a vermin-proof cowl, a moisture trap and a flow-sensing alarm that signals to the nurses' station if the scavenging flow falls below the rated value. The atmospheric discharge is typically not scrubbed in Australia (the environmental impact of the volatile anaesthetic agent on the local atmosphere is below regulatory threshold), but a charcoal capture column can be specified at premium for a teaching hospital with environmental-credential commitments.

Inspection is annual leak-tightness test with a halogen leak detector, two-yearly system pressure test, five-yearly borescope of inaccessible duct sections. Common failures are dried-out connector seals and pinhole corrosion at any duct section that is the wrong material specification. Exposure measurement is annual passive-sampler assessment of isoflurane (Safe Work Australia 50 ppm) and sevoflurane (no formal WES, target below 2 ppm), with nitrous oxide measurement if nitrous is in use (Safe Work Australia 25 ppm).

Exotic animal hospitals and zoo veterinary facilities

The exotic animal hospital handles species outside the normal small-animal and large-animal spectrum: zoo overflow exotic mammals, wildlife rehabilitation (kangaroos, wombats, possums, koalas), exotic birds (raptors, parrots, waterfowl) and reptiles. The major Australian exotic animal facilities are the Lort Smith Animal Hospital wildlife wing in Melbourne, Currumbin Wildlife Hospital in Queensland, Australia Zoo Wildlife Hospital at Beerwah, the Healesville Sanctuary clinical facility, the Taronga Conservation Society facilities at Mosman and Western Plains Dubbo, and the Zoos Victoria veterinary services at Werribee Open Range Zoo and Melbourne Zoo.

The HVAC brief is segmented by species and by clinical workflow. The wildlife admission and triage area is the highest-volume zone — Currumbin Wildlife Hospital admits over 9,000 cases per year — and is conditioned at 22 to 23 degrees Celsius, 8 to 10 ACH, NC 40 acoustic, with stainless extract because of high admission throughput and the disinfection routine between cases. The species-specific wards are conditioned to the species thermal envelope: reptile wards at 26 to 30 degrees Celsius with localised basking-zone heat lamps, bird wards at 22 to 26 degrees Celsius, marsupial wards at 18 to 22 degrees Celsius for adults and 26 to 30 degrees Celsius for orphaned joey nursery.

Psittacosis (Chlamydia psittaci) is the dominant zoonotic biosecurity concern. The disease is notifiable in all Australian states and a confirmed case in a wildlife hospital triggers a public-health response. The bird ward operates with dedicated AHU, no recirculation to other zones, and HEPA H13 on the supply where the ward routinely handles psittacine species. Dust extraction at the cage face captures feather dander and substrate particulate.

The zoo veterinary clinical facility (Taronga, Werribee Open Range, Melbourne Zoo, Australia Zoo) handles species ranging from frogs to elephants. The clinical brief unions the small-animal and large-animal programs in this guide, with the additional consideration that some species (giraffe, elephant, large ungulate) cannot be moved off the exhibit and must be examined in situ. The HVAC engineering for the on-exhibit field-veterinary work is mobile rather than fixed, but the clinical facility itself is conditioned to a multi-species program at 8 to 12 ACH with species-segregated wards.

Ductwork material is 304 stainless throughout the exotic hospital extract, transitioning to 316L stainless in necropsy, isolation and pharmacy compounding. The cleaning chemistry is sodium hypochlorite at 1,000 to 5,000 ppm available chlorine between species and at end of shift, and the duct material must handle that chemistry over the design life.

University veterinary teaching hospital infrastructure

The seven Australian university veterinary teaching hospitals are a distinct market segment in the veterinary HVAC market. Each combines clinical referral practice, undergraduate teaching and graduate research, with HVAC briefs that union the three programs.

University of Sydney School of Veterinary Science operates the Camden Veterinary Teaching Hospital at the rural NSW Camden campus (equine, livestock, exotic, wildlife) and a small-animal facility at the Camperdown inner-Sydney campus. Camden runs the equine surgical and medical referral service for the greater Sydney catchment, including racing-thoroughbred work from the Hunter Valley and the Randwick metropolitan stables. The Camden hospital is currently undergoing successive capital works expansions including a new equine surgery wing and an isolation barn upgrade.

University of Melbourne Faculty of Veterinary and Agricultural Sciences operates the U-Vet Hospital at the Werribee campus, the largest veterinary teaching hospital in Victoria. The facility delivers small-animal, equine, livestock and exotic services, with full referral capability in orthopaedic surgery, soft-tissue surgery, internal medicine and oncology. The equine hospital is integrated with the racing-thoroughbred catchment from the metropolitan Melbourne trainers (Caulfield, Flemington, Mornington) and the regional Victorian thoroughbred industry.

University of Queensland School of Veterinary Science operates the UQ Veterinary Medical Centre at Gatton, west of Brisbane, serving the Queensland equine industry (including the Gold Coast Magic Millions sales catchment), the QLD beef and dairy industry and the regional wildlife and exotic work. The Hendra virus risk profile is the highest in Australia at this facility and the isolation barn infrastructure is the most developed.

Murdoch University School of Veterinary Medicine operates The Animal Hospital Murdoch in Perth, serving the WA small-animal, equine and exotic referral market and the state-wide livestock industry. The hospital includes a full referral specialty program and an isolation facility for biosecurity work on the WA borders.

James Cook University College of Public Health, Medical and Veterinary Sciences operates the JCU Veterinary Medical Centre in Townsville, serving the North Queensland market. The clinical case mix includes a high proportion of tropical-zoonosis suspect cases (Hendra, equine encephalitis, Murray Valley) and the isolation infrastructure is correspondingly substantial.

Charles Sturt University Veterinary Science operates the veterinary science clinical facility at Wagga Wagga NSW, serving the regional NSW agricultural industry and the Riverina equine catchment. The facility delivers livestock and equine referral capability with a teaching mission focused on regional and rural practice.

University of Adelaide Veterinary Science operates the relatively recent (2008) veterinary teaching facility at Roseworthy SA, serving the South Australian agricultural and equine market. The facility is the youngest of the seven and the HVAC infrastructure reflects current practice in animal-facility design.

The mechanical engineer designing a teaching hospital expansion or refit reads the brief as the union of three programs and designs the AHU configuration, the duct riser layout and the extract train accordingly. The fabricator quoting a university tender quotes the union of all three.

Equine referral hospitals and racing-thoroughbred clinics

The private equine referral hospital sector is concentrated in three catchments: the Sydney metropolitan and Hunter Valley NSW corridor, the Melbourne metropolitan and regional Victorian network, and the Gold Coast Queensland thoroughbred sales corridor.

Randwick Equine Centre in Sydney is the largest racing-thoroughbred clinical facility in Australia, embedded in the Randwick training precinct and serving the NSW racing industry. The clinical brief includes routine racing-medicine, orthopaedic specialty surgery, advanced diagnostic imaging (MRI, CT, scintigraphy) and emergency response for the on-track racing population.

Scone Equine Hospital in the Hunter Valley NSW is the major referral hospital for the regional thoroughbred breeding industry, with specialty capability in reproduction, foal medicine, orthopaedic surgery and respiratory medicine. The Hunter Valley equine catchment is one of the major thoroughbred breeding regions globally.

Sydney Equine Hospital, WyEast Hospital and the network of metropolitan Sydney equine practices serve the urban equine population (recreational, sport horse, dressage, eventing) and the racing-stable medicine catchment for the on-course Sydney racing.

Goulburn Valley Equine Hospital, Avenel Equine Hospital, Eureka Equine, Mornington Equine, Werribee Equine Centre and the Equine Pavilion at Maddingley VIC serve the Victorian equine catchment with referral specialty work. Mornington Equine and Werribee Equine support the Caulfield and Flemington racing population; Goulburn Valley and Avenel support the regional sport-horse and racing population.

Magic Millions clinic at the Gold Coast and the Karaka clinic at the New Zealand Magic Millions sales complex deliver pre-sales clinical assessment, post-sales medicine, surgical referral and emergency response during the major sales fortnight each year.

Living Legends Greenvale VIC is the retirement and rehabilitation facility for retired thoroughbred racehorses, with veterinary infrastructure to support the ongoing geriatric medicine and end-of-life care for the resident population.

Inglis Riverside Stables at Warwick Farm Sydney is the major thoroughbred sales and training complex with on-site veterinary infrastructure to support the sales programme and the resident training population.

The HVAC brief for each of these facilities is the private-equine-referral subset of the university teaching hospital brief — full equine clinical service without the teaching and research overlay. The fabricator who serves one of these facilities is positioned to serve the others; the briefs are highly transferable across the catchment.

Charitable and major-animal hospitals

Lort Smith Animal Hospital at North Melbourne is the largest not-for-profit animal hospital in Australia, with a clinical caseload spanning small-animal companion medicine, exotic and wildlife rehabilitation and a substantial subsidised-service mission. The facility operates at AVA Hospital of Excellence tier and the HVAC infrastructure is correspondingly substantial.

RSPCA Animal Hospitals operate in most Australian states with clinical infrastructure supporting the inspectorate, the shelter operation and the subsidised veterinary service. The largest RSPCA hospitals (QLD at Wacol, NSW at Yagoona, Victoria at Burwood East) operate at AVA Hospital tier with full surgical, medical and isolation capability.

Zoos Victoria Veterinary operates clinical infrastructure at three sites: the Werribee Open Range Zoo, the Melbourne Zoo and the Healesville Sanctuary. The brief unions the exotic animal hospital program with the zoo veterinary clinical program and the wildlife rehabilitation program at Healesville.

Taronga Conservation Society operates clinical infrastructure at Taronga Mosman and Taronga Western Plains Dubbo NSW, supporting the zoo veterinary program and the conservation research program.

Currumbin Wildlife Hospital at Gold Coast QLD is the largest wildlife-specific veterinary hospital in Australia by case volume (over 9,000 cases per year), with infrastructure focused on triage, treatment and rehabilitation of injured Australian native wildlife.

Australia Zoo Wildlife Hospital at Beerwah QLD is the rehabilitation-oriented wildlife hospital associated with the Australia Zoo conservation programme, with substantial koala chlamydia treatment capacity and broader wildlife casework.

The HVAC brief for each of these facilities is the exotic and wildlife subset of the teaching hospital brief, with the charitable funding constraint shaping the as-built specification toward proven engineering rather than premium options.

Corporate veterinary groups and regional production-animal practice

Australian large animal veterinary practice is fragmented at the production-animal end and consolidated at the equine and small-animal end. The corporate consolidators in the broader veterinary market include Greencross Vets (the largest, with 170-plus practices nationally, focused on small-animal and emerging mixed-practice), VetPartners Australia and the legacy National Veterinary Care brand (now consolidated under Greencross).

The production-animal sector has its own corporate operator: Apiam Animal Health (ASX:AHX), the listed livestock-and-production-animal veterinary group with practices across regional Australia focused on dairy, beef cattle, sheep, swine and poultry medicine. Apiam practices are typically AVA Standard or Hospital tier with substantial production-animal infrastructure (handling crushes, cattle yards, processing race), and the HVAC brief is dominated by the agricultural-grade ventilation in the handling areas with smaller clinical zones for consultation and surgical work.

Pacific Vetcare operates a regional NSW-centred veterinary group with mixed small-animal and large-animal practice across the Mid North Coast catchment.

The HVAC brief for the production-animal practice is the agricultural-grade subset of the teaching hospital brief, with the bulk of the linear-metre run in galvanised duct on agricultural ventilation and the clinical zones in stainless on the small-animal specifications.

Industry bodies and accreditation

Australian Veterinary Association (AVA) is the peak professional body and operates the Hospital Accreditation Scheme at Standard, Hospital and Hospital of Excellence tiers. The scheme is voluntary but is the de facto industry benchmark for clinical infrastructure.

Equine Veterinarians Australia (EVA) is the AVA special-interest group for equine practice and publishes guidelines on equine hospital infrastructure that the mechanical engineer reads alongside the AVA accreditation criteria.

Australia New Zealand College of Veterinary Scientists (ANZCVS) is the specialist-college body for postgraduate veterinary qualification and publishes specialty-college standards (surgery, internal medicine, anaesthesia, pathology) that inform the room schedule for any practice operating at specialist-referral level.

The international references that the Australian designer reads alongside the Australian framework are the Royal College of Veterinary Surgeons (UK) for the British practice infrastructure tradition and the American Association of Veterinary Medical Colleges (US) for the comparable US teaching-hospital model.

Equipment vendors and clinical infrastructure

The major clinical equipment vendors who interface with the HVAC scope across the large animal practice include Smiths Medical (anaesthesia delivery, ventilation, infusion pumps), Datex Ohmeda (anaesthesia delivery and monitoring), Idexx Laboratories (clinical pathology bench analysers and reference laboratory services). The HVAC engineer coordinates with the equipment vendor at the design stage to understand the anaesthetic gas scavenging connection geometry, the equipment heat load and any specific room conditioning requirement (some equipment, particularly the pathology analysers, has a tight ambient temperature specification).

Duct material decision matrix — large animal practice

Pulling the material specification together across the practice room program:

• Galvanised steel coil to AS 4254 (0.55 to 1.5 mm wall): reception, owner waiting, offices, classroom and demonstration zones in the teaching hospital, supply ducts in clinical rooms upstream of the room boundary (because supply air is filtered and not in contact with biological contamination), supply ducts in the hospital ward stables, tack room, hay store, vet ambulance bay. Cost-effective, widely supplied, fabricated on the SBKJ SBAL-V auto duct production line in galvanised configuration.
• Stainless 304 (0.55 to 1.5 mm wall): hospital ward stable extract, induction stocks extract, hot-walker extract, exotic ward extract, fume cupboard extract through the lab envelope (upgrading to 316L for long-term formaldehyde exposure), BSC exhaust through the PC2 lab envelope, surgical supply downstream of HEPA, sterile storage supply, compounding room general extract, cattle and sheep handling crush extract where ammonia exposure is sustained. Resistant to ammonia, chlorhexidine, quaternary ammonium and routine sodium hypochlorite at 100 to 1,000 ppm. Fabricated on the SBKJ SBAL-V configured for stainless coil.
• Stainless 316L (0.55 to 1.5 mm wall): equine surgical theatre extract, anaesthesia recovery box extract, wash bay extract, equine MRI suite extract where applicable, isolation barn ductwork throughout (supply, extract and PPE lobby), necropsy room ductwork throughout, pathology fume cupboard exhaust where formaldehyde exposure is sustained, sterilising department dirty-side and steam-vent ductwork, mortuary refrigerated storage extract, on-site cremation room ductwork, anaesthetic gas scavenging line throughout. Resistant to chloride pitting under sodium hypochlorite at 1,000 to 10,000 ppm, formaldehyde decomposition products, decomposition acidic chemistry, halogenated anaesthetic decomposition products and steam-vent saturated chemistry. Fabricated on the SBKJ SBAL-V configured for stainless coil, with TIG-welded longitudinal seams using the SBKJ Stitch Welder (SBSW-30-2Z) for the fully-welded specification on isolation barn and HEPA housing components.
• Spark-resistant brass-bronze trim: anaesthetic gas scavenging path on rotating components, compressed-gas plant room ventilation fittings, any duct path where AS/NZS 60079 hazardous-area classification applies. The duct itself is stainless; the spark-resistant trim is on the rotating components and the bearing housings.

External insulation is by mineral wool to AS/NZS 4859 lagged with foil-laminated facing, sized for the supply air temperature relative to the ceiling-void ambient. Internal acoustic lining is acceptable in owner waiting, reception, office and staff zones only — never in surgical, treatment, ward stable, wash bay, isolation barn, necropsy, sterilising or compounding ducts because biological deep-cleaning will not reach internal lining.

Acoustic specification across the practice

Setting acoustic targets in a single table for clarity:

• Reception and owner waiting: NC 40. Distressed owner population, calm voice work needed.
• Consult bays (where present in the large animal practice — most equine work is in the laneway and stocks rather than in a consult room): NC 35.
• Equine surgical theatre: NC 35. Surgical concentration. Diffuser whine the most common acoustic complaint.
• Orthopaedic cleanroom-grade suite: NC 30. Fine-motor surgery under magnification.
• Anaesthesia recovery box: NC 35. Calm recovery accelerates clinical outcome.
• Hospital ward stables: NC 40. Horse sensitivity to noise; calm ward accelerates recovery.
• Isolation barn: NC 45. High-rate extract drives the noise floor; calm work for staff and patient.
• Necropsy: NC 45. Bone saws and high-pressure wash drive the noise floor.
• Wash bay: NC 40. Water spray and grooming activity intrinsic to the room.
• Hot-walker and treadmill: NC 45. Treadmill or hot-walker dominates.
• MRI scan room: NC 40, RF-isolated. Scanner noise floor dominant during scan.
• CT scan room: NC 40. Scanner noise floor dominant.
• Clinical pathology and histology lab: NC 40. Bench-and-cupboard noise floor sets the limit.
• Central sterilising department: NC 35 clean side, NC 40 dirty side.
• Pharmacy and compounding: NC 35.
• Tack and feed storage: NC 45. Not a sustained-occupancy zone.
• Cattle and sheep handling crush: NC 50 or higher. Crush hydraulics and cattle vocalisation dominate.
• Vet ambulance bay and float park: NC 50 or higher. Outdoor or semi-outdoor environment.

Achieving these targets is the duct silencer engineer's responsibility, working back from the diffuser face through the supply branch to the air handling unit. The duct fabricator's contribution is making sure the seam construction, the joint sealant and the supports do not introduce flanking noise that bypasses the silencer.

Commissioning the large animal practice HVAC

Commissioning is the closure step on every veterinary fit-out and the step on which AVA accreditation, state Veterinary Practitioners Board premises registration, Biosecurity Queensland Hendra protocol compliance and the practice owner's confidence all depend. The commissioning protocol covers air change, pressure regime, temperature stability, anaesthetic gas exposure, formaldehyde exposure, acoustic measurement and duct leakage.

• Air change verification. Calibrated balometer at every supply and extract diffuser in every room. Record the design rate, the measured rate and the tolerance (typically plus or minus 10 per cent of design). Repeat annually.
• Pressure regime verification. Digital manometer at every door between zones of different pressure — particularly the isolation barn (minus 15 Pa), PPE lobby (plus 5 Pa relative to barn), necropsy (minus 30 Pa), surgical theatre (plus 10 to 15 Pa) and CSSD pressure cascade. Record the differential, the design target and the door state (open and closed). Repeat quarterly in surgical, isolation and CSSD zones, annually elsewhere.
• Temperature and humidity stability. Seven-day temperature and humidity log in every clinical room. Record setpoint, achieved range and any deviations. Repeat annually.
• Anaesthetic gas exposure measurement. Passive samplers worn by anaesthetic-machine operators or a real-time photoacoustic monitor in the surgery suite. Record isoflurane (target below Safe Work Australia 50 ppm) and sevoflurane (target below 2 ppm) concentrations. Repeat annually or after any anaesthetic machine change.
• Formaldehyde exposure measurement. Passive samplers worn by necropsy and histology staff. Record concentration against Safe Work Australia 1 ppm STEL and 0.3 ppm TWA. Repeat annually.
• Ammonia measurement. Passive samplers or real-time photoionisation detector measurement in ward stables, handling crush and isolation barn. Record against Safe Work Australia 25 ppm STEL and 17 ppm TWA. Repeat annually.
• HEPA filter challenge. In-situ DOP or PAO challenge of every HEPA filter on the isolation barn exhaust and the necropsy room exhaust. Confirm efficiency above 99.95 per cent at MPPS per AS 4260 and ISO 14644-3. Repeat annually.
• Acoustic measurement. Sound-level meter at every clinical bench and surgical position. Record NC level achieved against design target. Repeat after any duct or AHU change.
• Duct leakage test. SMACNA seal class A leakage test (pressurise the duct section to 500 Pa, measure the leakage rate) at every shop-fabricated section and at every site-installed joint. Pressure-decay leak test on isolation barn ductwork to confirm leak rate below 0.05 per cent of system volume. Repeat after any duct alteration.

The commissioning package — a bound report with all nine test results, the as-built drawings, the AHU sequence-of-operations and the maintenance schedule — is the document the AVA inspector reads, the state veterinary board references, the Biosecurity Queensland inspector verifies and the practice owner files. Skipping it costs the practice the accreditation and costs the fabricator the next referral.

Why SBKJ machines are the correct line for large animal veterinary fabrication

The large animal veterinary fabricator delivers a mixed material brief: 30 to 40 per cent galvanised by linear metre (for supply across the practice and for owner waiting and office zones) and 60 to 70 per cent stainless 304 and 316L (for extract on every clinical zone, isolation, necropsy, wash bay and surgical theatre). The stainless ratio is substantially higher than in small-animal practice because the room volumes are bigger, the cleaning chemistry is more aggressive and the material upgrades pay back over the longer design life of a major teaching hospital or referral hospital. The machine line that serves this brief efficiently has three elements.

SBAL-V auto duct production line

The SBAL-V is the SBKJ U-shape automatic duct production line for rectangular ductwork. The line integrates uncoiling, levelling, beading, notching, shearing and TDF or angle steel flange forming in a single coil-to-duct workflow operated by 2 to 3 staff. Models SBAL-V-1250J and SBAL-V-1500J handle galvanised, stainless and aluminium coil from 0.5 to 1.5 millimetres thickness at coil widths up to 1,250 or 1,500 millimetres, forming speed 16 metres per minute, overall dimensions 14,000 by 2,000 by 1,800 millimetres (1250 variant) or 14,000 by 2,200 by 1,800 millimetres (1500 variant), connected load 87 kilowatts, machine weight 16 tonnes, power supply 380 V 50 Hz 3-phase. The operator enters duct dimensions on the PLC touchscreen and the line completes the Pittsburgh lock forming, TDF or angle flange forming and folding automatically — typical changeover between sizes is under one minute.

The SBAL-V is the workhorse machine for the large animal veterinary fabrication shop. Configured for galvanised it produces the supply ducts for the entire practice; reconfigured for 304 stainless it produces the hospital ward stable extract and the general clinical extract; reconfigured for 316L stainless coil it produces the isolation barn, wash bay, necropsy and surgical extract. The coil-changeover is a 20 to 30 minute operation on the SBAL-V and the daily fabrication schedule typically batches the galvanised work first, then the 304, then the 316L to minimise the number of coil changes per shift.

Stitch Welder (SBSW-30-2Z)

The SBKJ Stitch Welder is the intermittent stitch welding machine for joining sheet metal panels — used to produce a series of weld spots along seams that reduce heat input while maintaining strength. Model SBSW-30-2Z handles tube diameters 100 to 1,000 millimetres, welding length 50 to 1,000 millimetres, overlap 6 millimetres, material thickness 0.4 to 1.0 millimetres, welding speed 2 metres per minute, copper electrode diameter 20 millimetres, maximum power 40 kilowatts, machine weight 850 kilograms, mainframe dimensions 2,300 by 800 by 1,300 millimetres, power supply 380 V 50 Hz 3-phase. The machine welds galvanised, stainless 304 and 316L and aluminium-coated steel.

The Stitch Welder supplies the welded longitudinal seam on the stainless extract ductwork — Pittsburgh seam construction is acceptable on most large animal extract but the welded specification is required on the isolation barn (Hendra protocol, pressure-decay leak rate below 0.05 per cent of system volume), the necropsy room (formaldehyde and hypochlorite chemistry over the design life) and the HEPA filter housings (welded 316L stainless construction). The Stitch Welder is the dedicated machine for these critical seams in the large animal practice fabrication shop.

Round Tube Flanging Machine SBSF-1525

The SBKJ Round Tube Flanging Machine SBSF-1525 produces flanged edges on round duct ends — the bolted angle iron rings that connect spiral duct sections, particularly for higher pressure ratings or service-removable joints. The machine handles black steel 0.5 to 2 millimetres and stainless 0.5 to 2.5 millimetres at flanging widths 75 to 152 millimetres, maximum weight capacity 360 kilograms, processing diameter 100 to 2,000 millimetres, connected load 2.5 kilowatts, machine weight 520 kilograms, overall dimensions 2,200 by 1,100 by 1,240 millimetres, power supply 380 V 50 Hz 3-phase.

The SBSF-1525 produces the bolted flanged terminations on the round duct in the large animal practice — the supply diffuser bank to the equine surgical theatre at 800 to 1,200 millimetres diameter, the isolation barn riser at 400 to 600 millimetres diameter, the HEPA filter housing inlet and outlet flanges, and the spark-resistant scavenging line terminations. The bolted flange allows service-removable connection at every HEPA housing for filter change and at every spark-resistant trim on the scavenging path for periodic inspection.

Optional add-ons that improve the fabricator's competitiveness on large animal tenders: a TIG longitudinal seam-welding station for fully-welded 316L stainless on isolation barn ductwork (an upgrade beyond the stitch-welded Pittsburgh seam, used in the most rigorous biocontainment specifications); an automated insulation feeder for externally-insulated galvanised supply duct (saves 20 to 30 per cent of the labour budget on a teaching hospital fit-out); a CNC plasma cutting station for stainless transitions, take-offs and irregular fittings on the equine surgical theatre supply geometry.

The line accepts coil from Australian steel merchants on either Pittsburgh seam (SBAL-V) or fully-welded longitudinal (Stitch Welder), and produces ductwork to SMACNA seal class A, AS 4254 construction class A and the leakage rates implied by AS 1668.2 ventilation regimes. The output is suitable for AVA Hospital of Excellence tier facilities, university teaching hospital infrastructure, equine referral and racing-medicine practice, and the Biosecurity Act Hendra protocol isolation barn requirement.

SBKJ provenance — Box Hill North VIC and 30 years of HVAC duct machinery

SBKJ Group operates from Box Hill North VIC and has been manufacturing HVAC ductwork machinery since 1995. The factory holds ISO 9001:2015 quality management certification and CE marking under Machinery Directive 2006/42/EC. The installed base is over 5,000 machines in 100+ countries, with Australian after-sales support delivered direct from the Box Hill North office.

For Australian large animal veterinary projects the support model is direct: an SBKJ engineer reviews the fabricator's room schedule on any veterinary teaching hospital, equine clinic or large animal hospital project, confirms the material specification, the seam type and the line setup required, and quotes the machine configuration. The reply window is 12 hours. The commissioning visit is 7 days included in the machine price, and the warranty is 12 months on mechanical and electrical components with lifetime spare parts continuity.

The strategic position SBKJ holds in the large animal veterinary HVAC market is straightforward: we are the machine supplier that already knows the brief. Whether the project is a university teaching hospital expansion, an equine referral hospital fit-out, a Hendra isolation barn retrofit or a racing-thoroughbred clinic upgrade, the duct fabricator on each project is running an SBAL-V configured for galvanised plus stainless coil, a Stitch Welder for the critical welded seams and an SBSF-1525 for the bolted flanges. The standard 30/70 T/T payment terms apply, the line ships from Box Hill North VIC with seafreight via the Port of Melbourne or Sydney, and the commissioning engineer attends the customer's workshop in person for the duration of the start-up phase.

How SBKJ supports the large animal HVAC fabricator

SBKJ Group serves the large animal veterinary HVAC ductwork market through three channels:

• Machine supply. SBAL-V auto duct production line, Stitch Welder (SBSW-30-2Z), Round Tube Flanging Machine SBSF-1525, with stainless coil optionality where the fabricator's order book includes teaching hospital, equine referral or biosecurity isolation barn work. Standard 30/70 T/T commercial terms, CE marked, ISO 9001:2015 audited, with Australian after-sales support from our Box Hill North VIC office.
• Engineering consultation. Our engineering team reviews the fabricator's room schedule for any large animal veterinary project and confirms the material specification, the seam type and the line setup required. Free, with no expectation of order. The cost to us is one engineer hour; the value to the fabricator is avoiding a stainless coil change-over on a deadline.
• Reference projects. We supply reference cases from our installed base of veterinary, dental, hospital and health-care HVAC fabricators. The case studies cover the room program, the air-change targets, the duct material decisions and the as-built outcomes. Available on request from our About page.

The next step for any mechanical consultant, practice owner, university capital works manager or duct fabricator with a current large animal veterinary brief is to talk to an SBKJ engineer. The 12-hour reply window applies, the engineer leads the conversation, and the response is a machine configuration matched to your specific project rather than a generic catalogue.

Discuss your veterinary teaching hospital or equine clinic duct line with an SBKJ engineer →

FAQ

What air change rate applies to an equine surgical stocks bay?

6 to 10 ACH with displacement ventilation, supply tempered to 18 to 22 degrees Celsius and a sloped floor with stainless drainage gully. Room volume 90 to 140 cubic metres for a single equine theatre bay because of the 4.2 to 4.8 metre ceiling needed for anaesthesia hoists. Supply at high-level perforated diffuser along the longitudinal axis, return at low level on the long walls, anaesthetic gas scavenging through 316L stainless to a dedicated roof stack.

How is Hendra virus risk addressed in HVAC for a Queensland or northern New South Wales equine clinic?

A dedicated single-pass isolation barn at minus 15 Pa relative to the corridor, 12 to 15 ACH, HEPA H13 on exhaust before atmospheric discharge, no recirculation, a dedicated PPE lobby at plus 5 Pa relative to the barn for clean gowning air, and a charcoal scrubber on the exhaust stack in Hendra-endemic catchments. Stack at least 7.5 metres from any intake and 3 metres above the highest roof. Ductwork 316L stainless throughout the envelope, fully welded longitudinal seams, pressure-decay leak rate below 0.05 per cent of system volume at commissioning.

What ductwork material is correct for an equine wash bay?

316L stainless from the grille face back at least 5 metres to the first riser, externally insulated to prevent ceiling-void condensation, TIG-welded longitudinal seams on the high-humidity extract sections. Galvanised fails in 12 to 18 months in this service; 304 stainless develops chloride pitting under hypochlorite-based disinfectants between cases.

What is the difference in HVAC brief between a teaching hospital and a private equine clinic?

A teaching hospital unions three programs: large animal clinical surgery at ASHRAE Chapter 11 rates, classroom and demonstration ventilation at AS 1668.2 occupied-room rates, and laboratory animal vivarium ventilation at AS/NZS 2243.3 PC levels. A private equine clinic delivers only the first program at a slightly lower air change rate. Both demand the same patient air-quality outcomes but the teaching hospital has higher peak occupancy in the same physical volume, which drives supply by 20 to 40 per cent.

How is an equine MRI or CT room conditioned?

Equine MRI at 22 to 24 degrees Celsius, 45 to 55 per cent RH, 6 to 8 ACH inside a Faraday cage with waveguide or copper-mesh-lined HVAC penetrations. Magnet quench vent is a separate large-diameter vent direct to atmosphere, sized by the manufacturer, never used for ventilation. Equine CT conditioned similarly at 6 ACH with cooling load dominated by the X-ray tube heat exchanger at 12 to 18 kilowatts continuous.

What ventilation rate applies to a 12-stall hospital ward stable block?

8 to 12 ACH per stall, 100 per cent outside air on exhaust side, never any recirculation between stalls. Supply at high level above the stall door at no more than 0.3 metres per second muzzle velocity, return at low level on the back wall. Each stall has its own supply branch and its own return branch — shared trunks are not acceptable because of cross-contamination of strangles, equine herpesvirus, rotavirus and other respiratory pathogens.

What is the necropsy room HVAC specification for a large animal post-mortem facility?

Minus 30 Pa relative to the corridor, 12 to 20 ACH at 100 per cent outside air, dedicated exhaust through HEPA H13 and activated carbon, downdraft post-mortem table at each work bay, supply 18 to 21 degrees Celsius, ductwork 316L stainless throughout because of formaldehyde fixation chemistry and sodium hypochlorite cleaning at 5,000 to 10,000 ppm available chlorine.

What SBKJ machines suit a large animal veterinary ductwork fabricator?

SBAL-V auto duct production line in galvanised configuration for general practice supply, switched to 304 and 316L stainless coil for wash bay, necropsy and isolation barn ductwork. Stitch Welder (SBSW-30-2Z) for fully-welded longitudinal seams on isolation barn and HEPA housing components. SBSF-1525 round tube flanging machine for bolted flanged terminations on isolation barn risers and equine theatre supply. Spark-resistant brass-bronze trim where anaesthetic gases are handled.