Veterinary Clinic and Small Animal Hospital HVAC Duct Guide

Why community veterinary HVAC is its own discipline

A community veterinary practice is not a hospital and it is not a research vivarium. It is something stranger: a retail-style storefront where members of the public sit in a waiting room with stressed cats, undisciplined dogs and the occasional cockatoo, while behind the consult-room door a clinician runs a small operating theatre with anaesthetic gases, surgical electrocautery, dental aerosols and a sterilising autoclave. The HVAC system has to keep all of those zones in the same building, separated by air, and it has to do so on the floor plan of a converted suburban shopfront with a 2.7 m ceiling and a single mechanical riser.

Most of the published HVAC literature on animal facilities — including our companion guide on veterinary, animal research and laboratory animal HVAC — focuses on research vivariums, PC2/PC3/PC4 biocontainment and university-scale animal hospitals. Community vets, 24/7 emergency clinics and specialty referral hospitals have a different problem set: high foot traffic, mixed species in a single building, surgical workload running in parallel with retail consults, anaesthetic gas exposure to non-clinical staff, kennel ammonia at clinically irritant concentrations and acoustic targets driven by dog vocalisation rather than rat respiration rates.

This guide is the engineering reference SBKJ delivers when the next project is a Greencross fit-out, an Animal Emergency Service 24/7 build, a SASH expansion or a regional GP refit. Every room type is covered with its air-change target, setpoint, pressure regime, material specification and acoustic limit, and the closing section maps it back to the SBKJ duct machine configuration that produces the ductwork most economically.

Regulatory framework — what governs a veterinary practice fit-out

Australian veterinary HVAC sits at the intersection of half a dozen documents. None of them is a single source of truth. The competent mechanical engineer reads them together.

• ASHRAE Applications Handbook, Chapter 9 (Health Care Facilities). The international design reference for procedure and surgical room ventilation. Veterinary surgery is not human surgery, but Chapter 9 air-change targets, filtration levels and pressure regimes are the accepted analogue used by Australian mechanical consultants when sizing a vet operating theatre. Treatment, dental and ICU rooms follow Chapter 9 principles at slightly reduced ACH compared with human equivalents.
• AS 1668.2 (Australian Standard for mechanical ventilation in buildings). Sets the minimum outdoor-air rate for occupied rooms. Consult rooms, waiting rooms, offices and staff rooms are sized at 10 L/s per person plus 0.6 L/s/m². AS 1668.2 also drives smoke-spill, smoke-control and corridor pressurisation arrangements for any veterinary build above the small-clinic threshold under the National Construction Code.
• AS/NZS 4254 (Ductwork for air-handling systems). Construction standard for galvanised and stainless steel ductwork, seam types, sealant classes, support and bracing. Veterinary fit-outs typically use seal class A construction for surgical, dental, kennel and cattery exhaust to limit leakage of anaesthetic gases and ammonia into ceiling voids and adjacent tenancies.
• AS 4187 (Reprocessing of reusable medical devices). Applies to veterinary surgical instruments through the same workflow as in 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 even though the standard was written primarily for human-health settings.
• AS 1668.1 (Fire and smoke control). Governs fire dampers, smoke dampers and the integration of HVAC ductwork with the building's passive and active fire-protection systems. Critical at every penetration of a fire-rated wall — the surgery suite, mortuary, drug storage room and kennel block are typically fire-separated from public reception areas.
• National Construction Code Volume One (Class 9a). Larger veterinary specialty and emergency hospitals are classified as Class 9a (health care) buildings under the NCC, attracting the more onerous mechanical ventilation, fire-engineering and accessibility provisions that apply to human hospitals. Single-suite community clinics in a Class 6 (commercial) retail tenancy are governed less stringently — the threshold is set by the consent authority and is worth confirming early.
• Australian Veterinary Association (AVA) accreditation. The AVA Hospital Accreditation Scheme audits practice infrastructure across three tiers: Standard (basic GP clinic), Hospital (full surgical and hospitalisation capability) and Hospital of Excellence (specialty, referral and emergency hospitals). The accreditation criteria specify the rooms that must be present, the equipment, the sterilising workflow and the ventilation expectations. Practices in pursuit of accreditation should be designed around the target tier from the outset.
• State Veterinary Practitioners Boards. Each Australian state licenses individual veterinarians and, in most cases, registers the premises from which they practise. The board may inspect facilities for compliance with state-specific guidelines on radiation safety (X-ray, CT, dental), Schedule 4 and Schedule 8 drug storage, anaesthetic safety and biosecurity. Premises registration is renewed annually in most states.
• NIOSH and Safe Work Australia anaesthetic gas exposure limits. The NIOSH occupational exposure limit for nitrous oxide is 25 ppm time-weighted average and for halogenated volatile anaesthetics (isoflurane, sevoflurane) 2 ppm. Many Australian practices target a lower internal limit. Compliance is achieved through active waste-gas scavenging, room ventilation and annual exposure measurement.
• EPA jurisdictional licensing. Cremation and high-volume mortuary operations may attract Environmental Protection Authority licensing in each state, separate from the practice's HVAC scope. Most veterinary practices outsource cremation to a specialist contractor and limit on-site mortuary to short-term refrigerated storage.

None of these are optional. The mechanical engineer who signs the certificate of compliance is the one who reconciles them at every room boundary.

Consult rooms — the heart of the practice

The consult room is the smallest billable space in a veterinary practice and the one a fit-out economy is most often imposed on. It is also the room where every member of the public spends 15 to 30 minutes face-to-face with the clinician and the patient. Get the consult room wrong and the practice rating on every online review platform drops by half a star within six months.

The room program: 12 to 16 m², typically 3.5 m by 4.0 m, with a consult bench, a clinician's workstation, a wall-mounted otoscope and ophthalmoscope, a refrigerated vaccine cabinet, hand basin and waste bin. Two to four occupants — the clinician, the owner, occasionally a vet nurse — and one to two patients, usually a dog or cat. Occasionally a rabbit, ferret, guinea pig, snake or bird.

The mechanical brief follows AS 1668.2: 10 L/s per person and 0.6 L/s/m². A 16 m² room at four occupants needs 40 L/s outdoor air plus 9.6 L/s area allowance, total 49.6 L/s minimum supply. At 2.7 m ceiling height the room volume is 43.2 m³, so the supply rate of 49.6 L/s delivers approximately 4.1 ACH — well below the practical target of 6 to 8 ACH. The system is therefore sized at 80 to 110 L/s of supply to deliver the upper-target air change.

Temperature setpoint 22 to 23 degrees Celsius, relative humidity 50 percent. Going colder than 22 is uncomfortable for an undressed cat on the bench in winter; going warmer than 23 is uncomfortable for the clinician under examination lighting. Humidity matters because dehumidified clinic air at 30 percent RH causes static-electric shocks on examination tables (cats hate this) and dries out canine corneas during ophthalmic examination.

The acoustic target is NC-35, the same as a recording studio control room. The reason is straightforward: anaesthesia consent conversations, oncology diagnoses and end-of-life euthanasia discussions all happen in the consult room. A noisy diffuser or a rattling damper makes those conversations harder. Sound-attenuated supply boots and a fully internally-lined diffuser plenum solve it; an under-sized branch with high face velocity does not.

Duct material in the consult room is galvanised steel to AS/NZS 4254. There is no clinical contamination risk in consult that mandates stainless. Cleaning is by surface wipe with quaternary ammonium disinfectant on the diffuser face only; the duct interior is sealed. Internal acoustic lining is acceptable for consult and waiting areas because biological deep-cleaning is not required.

Treatment, dental and induction — the working core

Behind the consult-room door is the treatment room (sometimes called "the back"), where the bulk of nurse-led care happens: blood draws, IV cannulation, wound dressings, bandaging, ear cleans, nail clips, anal-gland expression, microchipping and the staging area for surgical patients. In larger practices the dental table sits in the treatment room or in a dedicated dental room adjacent.

The mechanical brief steps up from consult. ASHRAE Applications Handbook Chapter 9 (health-care procedure rooms) is the analogue: 8 to 12 ACH, supply temperature 18 to 22 degrees Celsius, RH 45 to 55 percent. The room is at neutral to slightly negative pressure relative to the corridor (-5 Pa) to prevent the migration of dental aerosols, induction-stage anaesthetic vapour and electrocautery smoke into the consult and waiting areas.

Dental work in small animals is performed under general anaesthesia, almost always with an isoflurane vaporiser, and produces an aerosol of saliva, oral bacteria and water — the same aerosol that human dentists generate, with the same biological hazard. The dental table requires a dedicated extract grille within 600 mm of the patient's head, capturing aerosol at source before it disperses into the room. Active anaesthetic gas scavenging is connected directly to the anaesthetic machine via a 30 mm scavenging hose to a 316 stainless or hard-drawn copper line, separate from the room exhaust.

Induction is the room where the patient is sedated and intubated before being moved to the surgery suite. It is often combined with the treatment room in smaller practices. Whether combined or separated, induction needs the same air-change rate and the same anaesthetic gas capture, because mask-induction (most cats, exotics and difficult dogs) is the highest-leak step in any anaesthetic workflow.

Duct material in treatment and dental is stainless steel 304 from the grille face back at least 3 m to the first riser. The reason is twofold: dental cleaning with quaternary ammonium and citric-acid descaler agents, applied with high-pressure spray, will etch galvanised coating within 18 to 24 months; and the dental aerosol contains enough mineralised water and organic debris to seed biofilm in any porous internal surface. Stainless duct, externally insulated, internally smooth, is the correct specification.

Anaesthetic gas exposure measurement: an annual workplace assessment using passive samplers or a real-time photoacoustic monitor confirms compliance against the NIOSH 25 ppm nitrous oxide and 2 ppm halogenated anaesthetic limits. Where the practice does not use nitrous (most modern Australian small-animal practices have stopped using nitrous), only the halogenated assessment is needed.

The surgical suite — positive pressure done correctly

The surgical suite in a community veterinary practice is a smaller, simpler version of a human operating theatre. The same physical principles apply but the parameters are tuned for the patient population, the surgical workload and the budget envelope.

Air change rate: 10 to 15 ACH. Below 10 ACH the room cannot clear isoflurane and electrocautery smoke fast enough between cases; above 15 ACH the supply diffuser face velocity disturbs the surgical field and chills the patient. The room temperature is 18 to 22 degrees Celsius — colder than the rest of the practice — because the surgeon is gowned, gloved, masked and working under intense overhead lighting that adds 200 to 400 W of radiant heat. The patient is on a heat-circulating mat to prevent hypothermia.

Supply filtration is HEPA H13 minimum (99.95 percent efficient at 0.3 micron MPPS). H14 is preferred in specialty hospitals running orthopaedic implant surgery, where intraoperative bacterial contamination drives prosthetic joint infection rates. Supply distribution is by laminar-flow diffuser bank centered above the operating table, sized to deliver a 0.3 to 0.5 m/s vertical air curtain across the surgical field. Return is at low level on opposite walls, never directly above or beside the surgical table, to prevent contaminated room air being entrained into the laminar zone.

Pressure regime: +15 Pa relative to the corridor, verified at commissioning with a digital manometer and again at quarterly intervals. The positive pressure is what keeps corridor and recovery-room air from being drawn into the surgical suite every time the door opens. Door undercuts are not used in surgery; instead, transfer grilles in the wall above the door return air from the suite into the corridor at a controlled rate that maintains the pressure differential.

Anaesthetic gas scavenging: every anaesthetic machine in the surgical suite is connected to active scavenging. The scavenging line in the surgical suite is 316 stainless because halogenated anaesthetic decomposition products (trace amounts of carbonyl compounds, formaldehyde, hydrogen fluoride) attack 304 and galvanised material over a 10-year duct lifecycle. The line is sloped at 1:200 to a moisture trap and terminates to atmosphere at least 7.5 m from any building intake and 3 m above the roof line per typical AS 1668.2 dispersion rules.

Acoustic target: NC-30. Surgical concentration is fatigued by background noise. The most common acoustic complaint in a poorly-designed vet surgical suite is the diffuser whine at the high air-change rate — solved by reducing face velocity below 2.5 m/s, oversizing the diffuser plenum and acoustically lining the supply branch but not the diffuser face itself.

Duct material in the surgical suite is 304 stainless on supply (HEPA-protected) and 316 stainless on extract and anaesthetic gas scavenging. The supply duct is externally insulated to prevent condensation on the cold supply at the room boundary; the extract is bare stainless because internal insulation is incompatible with the chemical-cleaning regime applied to surgical exhaust under AVA Hospital of Excellence accreditation.

Recovery and ICU — the species-aware ward

The recovery and intensive-care areas of a community veterinary practice are where post-surgical and critically-ill patients spend their hospitalisation time. In a community GP clinic this is a single ward with 8 to 12 cages; in a 24-hour emergency hospital it is a full ICU with 20 to 40 cages, oxygen-supplemented cages, isolation, dialysis bay and a continuous-monitoring nursing station.

Temperature setpoint is wider than elsewhere in the practice — 22 to 26 degrees Celsius — because post-anaesthetic patients lose thermoregulation for hours after extubation, and small-breed dogs and cats below 4 kg cool below safe core temperature in any room below 24 degrees. ICU cages for critical patients have individual heating elements; the room HVAC sets the baseline.

Air change rate is 6 to 10 ACH with 100 percent outside air on the extract side. Recirculation between recovery and the rest of the practice is not permitted because of post-anaesthetic odour, gastrointestinal symptoms, vocalisation and the constant low-level shedding of skin and fur. Supply diffusers are placed above each bank of cages and the extract is at low level along the cage row to capture exhaled aerosols, urine vapour and faecal odour at the source.

Individual-cage HVAC is a feature of larger specialty hospital ICUs. Each cage has its own supply diffuser and its own return grille connected back to the AHU via a flexible duct connection at the cage wall. This allows the ICU clinician to isolate an individual cage on supplemental oxygen, on humidified air or on filtered air for an immune-compromised patient. The duct architecture is more complex but the clinical benefit is substantial in any hospital handling more than 200 hospital admissions per year.

Acoustic target NC-30 to 35 — the lower end is achievable because the patient population is sedated, but in the canine recovery area the dog vocalisation noise floor dominates anyway. Stress-reducing design (subdued lighting, low-traffic flow, acoustic-lined walls) does more for patient outcomes than over-engineering the ductwork. The HVAC contribution is making sure the supply diffuser does not whine.

Duct material is 304 stainless on extract (urine, faeces, disinfectant). Supply duct is galvanised, externally insulated, because supply air is filtered upstream and is not in contact with any biological contamination. Stainless is reserved for the dirty side.

Boarding kennels — ammonia, acoustics and air change

Most Australian community veterinary practices offer boarding for both medical convalescence and routine pet care. A boarding kennel is a separate room program from the medical ward: 6 to 20 runs, each typically 1.5 m by 2.0 m with a raised bed, water bowl and food bowl, separated by sealed dividing panels for biosecurity and visual stress reduction.

The dominant air-quality problem in a kennel is ammonia. Canine urine, when not removed within hours, hydrolyses to ammonia at concentrations that exceed the workplace exposure standard within an enclosed run. Field measurements in poorly-ventilated commercial kennels routinely show ammonia at 20 to 40 ppm at floor level — the workplace exposure standard is 25 ppm short-term and 10 ppm time-weighted average over an 8-hour shift, and dogs at ground level get the worst of it because ammonia is denser than air and pools at the floor.

Control is by three mechanisms operating together. First, mechanical ventilation at 6 to 10 ACH with 100 percent outside air on the exhaust side, never recirculated to other zones. Second, dedicated low-level extract grilles along the run frontage at floor level, capturing ammonia and CO₂ at the point of generation rather than after they have stratified the room. Third, supply diffusers at high level along the corridor wall, delivering tempered fresh air down into the run.

Acoustic target is NC-40, intentionally relaxed from the clinical areas because the dog vocalisation noise floor in a kennel is typically 70 to 85 dB(A) anyway. The acoustic priority is the wall and floor construction (concrete-block walls, sound-absorbing ceiling, sealed acoustic doors) not the duct silencer. The duct contribution is making sure the supply branch does not telegraph noise from one run into the next — solved by individual flex-duct runs to each diffuser, not a continuous slot diffuser shared across multiple runs.

Duct material is 304 stainless from the grille face back at least 3 m. Internal duct surface is exposed to ammonia, water-aerosol from hosing-down disinfection, and quaternary ammonium and chlorinated detergents in routine cleaning. Galvanised duct in this service fails by zinc etching within 24 to 36 months. Externally the duct is galvanised because the ceiling-void environment is benign.

Cattery — why cats need their own AHU

The single most common ventilation mistake in Australian small-animal practice design is sharing the air handling unit between the canine boarding area and the cattery. The mistake is made because the cattery is typically smaller than the kennel (4 to 12 cages versus 6 to 20 runs) and the obvious efficiency is to size one AHU for both.

Three reasons not to. First, cats are profoundly stressed by canine pheromones, canine vocalisation transmitted through shared ductwork, and the smell of dog urine in supply air. The clinical observation is that cats boarded in dog-shared-air catteries lose 5 to 10 percent of body weight in a 5-day stay and present with stress-induced lower-urinary-tract disease at 3 to 4 times the rate of cats in segregated catteries. Second, feline pathogens (feline herpesvirus type 1, feline calicivirus, Bordetella bronchiseptica, Mycoplasma felis) are aerosolised efficiently and survive in shared duct biofilms. Third, AVA Hospital of Excellence accreditation specifies separation of feline and canine ventilation.

The correct design provides a dedicated AHU for the cattery, on a dedicated extract riser, with a separate building penetration. Air change rate is the same 6 to 10 ACH and the temperature target is 21 to 24 degrees Celsius (slightly warmer than canine, because cats prefer it). The acoustic target is NC-35, lower than the kennel because the feline noise floor is much lower than the canine noise floor — a calm cattery is whisper-quiet.

Duct material is 304 stainless on extract (urine, litter dust, quaternary ammonium disinfectant). Supply is externally-insulated galvanised. The supply diffuser is fitted with a fine mesh insect screen at the riser termination because cats are extraordinarily skilled at extracting any insect that finds its way into a cage.

Bird and exotic-species wards — psittacosis and dust

Specialty referral hospitals and emergency hospitals in metropolitan Australia routinely admit birds, reptiles, ferrets, guinea pigs, rabbits and occasional zoo-overflow exotic mammals. The bird and exotic ward is the third leg of the segregated ventilation strategy, behind canine and feline.

The biosecurity driver is psittacosis (Chlamydia psittaci), a zoonotic bacterial disease transmitted from birds to humans through inhalation of dried faecal dust and feather dander. Psittacosis is a notifiable disease in all Australian states and a confirmed case in a veterinary practice triggers a public-health investigation, a 4 to 6 week quarantine on the affected ward and a thorough clinical work-up of staff and recent clients. Containment is by ventilation: separate AHU, separate extract, no recirculation to other zones, and HEPA filtration on the supply if the ward routinely handles psittacine species (cockatoos, macaws, parakeets, lorikeets).

The second design problem in a bird ward is dust. Cockatoo dander, feather dust, seed husk fragments and substrate particulate clog standard diffusers within weeks. The design response is dust extraction at the cage face — a localised extract grille within 600 mm of each cage door — captured into a stainless duct with an inline particulate filter accessible from the corridor side for routine replacement.

Temperature setpoint varies by species program. Most psittacine and passerine birds are housed at 22 to 26 degrees Celsius; reptiles in dedicated reptile rooms at the species-specific thermal gradient (typically 24 to 32 degrees Celsius); small-mammal exotics at 20 to 24. The exotic ward HVAC therefore typically delivers tempered air at 24 degrees and species-specific micro-environments are achieved at the cage level with heat lamps, ceramic emitters and supplemental cage HVAC.

Air change rate is 8 to 12 ACH because of the dust load. Duct material is 304 stainless on extract; 316 on any extract from a psittacosis-suspect isolation cage. Acoustic target NC-35; bird vocalisation is intermittent but loud, and an oversized supply diffuser bank delivers the rated air change at low face velocity to keep the supply path quiet.

Surgical specialty suites — orthopaedics, ophthalmology, oncology, neurology

Specialty referral hospitals in metropolitan Australia run dedicated surgical suites for ophthalmology, orthopaedics, oncology, neurology, cardiology and soft-tissue specialty surgery. Each specialty has subtly different HVAC requirements layered on top of the general surgical-suite specification.

Ophthalmology. Ocular microsurgery is performed under operating-microscope magnification at 4× to 25×. Air movement at the surgical field must be minimal because corneal drying is rapid at any face velocity above 0.15 m/s on the eye surface. The supply diffuser is upsized and positioned to deliver air down at the surgeon's shoulders, not at the patient's face. Temperature 21 to 22 degrees Celsius. NC-30 acoustic — the surgeon is using a foot-pedal phacoemulsifier and ear-clear concentration matters.

Orthopaedics. Joint replacement, fracture repair with implants, and arthroscopy are the highest-risk procedures for surgical-site infection. HEPA H14 supply, laminar-flow diffuser bank directly above the surgical field, +20 Pa pressure differential to corridor, 15 to 20 ACH (towards the upper end of the surgical range), and 304 stainless on extract for compatibility with hospital-grade disinfection. Specialty hospitals also typically gown surgical staff in disposable single-use suits with internal exhaust to avoid shedding bacteria into the laminar zone.

Oncology surgery. Surgical oncology in dogs and cats includes radical mastectomy, splenectomy, hepatic and pulmonary lobectomy, intracranial mass removal and limb-sparing osteosarcoma surgery. The HVAC parameters match general surgery. The adjacent oncology chemotherapy compounding suite, by contrast, requires a Class II biological safety cabinet vented to atmosphere through HEPA-and-carbon, with the surrounding room at negative pressure, because cytotoxic preparation generates an inhalation hazard for staff.

Neurology and neurosurgery. Intracranial surgery requires the same H14 filtration and laminar-flow specification as orthopaedics, with the addition of acoustic NC-25 in the suite — the lowest target in the practice — because intraoperative neurological monitoring (electroencephalography, evoked potentials) is sensitive to mains-frequency electromagnetic noise from HVAC motors and contactors. Variable-speed-drive motors with shielded cabling and a grounded duct earthing strap address this.

Imaging — X-ray, ultrasound, CT and MRI

Diagnostic imaging in community vet practice is dominated by general radiography and ultrasound; in specialty hospitals it extends to CT and MRI. Each modality has its own HVAC characteristics.

X-ray and dental radiograph rooms follow general treatment ventilation (8 to 10 ACH, neutral pressure, 22 degrees) with the addition of lead-shielded wall construction. The lead shielding affects duct routing only inasmuch as any wall penetration must be lead-lined to preserve the room's radiation containment rating. Penetration design is by the radiation safety consultant; the HVAC engineer details the duct sleeve and the radiation-physicist signs off on the as-built penetration.

Ultrasound rooms are general-purpose consult-equivalent with the addition of low ambient lighting (dimmable, 50 to 200 lux at the bench). Air-change rate 6 to 8, temperature 22 to 23, NC-35 acoustic.

CT scanners are large, heat-generating installations — a typical 64-slice scanner dissipates 12 to 18 kW continuously. The scan room is on a dedicated air conditioning circuit sized for the load. Air-change rate is set by occupancy (typically 6 ACH) but the cooling capacity dominates the design. Acoustic NC-40 — the scanner noise floor is dominant during a scan.

MRI installations in veterinary specialty hospitals are 0.4 T to 1.5 T systems, occasionally 3 T in research-affiliated centres. The MRI scan room is inside a Faraday cage (copper or galvanised steel sheeting laminated into the wall and ceiling) to exclude radio-frequency interference. Any HVAC penetration of the Faraday cage requires either a waveguide (a length of conductive duct that is much longer than its diameter, attenuating RF) or a fully copper-mesh-lined duct boot with a 360-degree grounded contact. The magnet quench vent — the emergency vent that releases helium gas if the magnet quenches — is a separate, large-diameter vent direct to atmosphere, not part of the HVAC system. The vent is fail-safe open and is never used for ventilation purposes.

Pharmacy, drug storage and compounding

The veterinary pharmacy is a hybrid retail-and-clinical space. Schedule 4 (prescription-only) medicines are dispensed across the consult-room interface; Schedule 8 (controlled drugs — ketamine, methadone, buprenorphine, fentanyl, morphine, midazolam) are stored in a tamper-proof cabinet with an audit-logged access record, in a separately ventilated bunded room.

Ambient HVAC for the pharmacy 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's compressor cycle is predictable.

Compounding bench — where individual prescriptions are made up from bulk medicines — uses a Class II biological safety cabinet for cytotoxic preparation (oncology chemotherapy) 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 relative to the corridor (-10 Pa) to contain any aerosolised compound to the room.

Duct material in the compounding extract is 316 stainless because cytotoxic and citric-acid compounds attack 304 over time. The extract runs to atmosphere directly through the roof at least 3 m above the ridge line and 7.5 m from any intake.

Mortuary and euthanasia rooms

Every veterinary practice has a euthanasia room — the dedicated space where end-of-life consultations and procedures happen. In a community GP clinic this is often the consult room used quietly between cases; in specialty and emergency hospitals it is a dedicated room with subdued lighting, an extracted-air register and a private corridor exit to a parking bay where the owner can leave without re-entering the waiting room.

The HVAC brief is straightforward: 8 to 10 ACH, dedicated exhaust to atmosphere (never recirculated), 22 to 23 degrees Celsius, NC-30 acoustic. The exhaust ducts the euthanasia procedure's volatile anaesthetic vapour (pre-euthanasia sedation typically uses propofol or alfaxalone, but volatile anaesthetic is used for mask induction in some cases) and the post-mortem decomposition gases away from the public-facing zones of the practice.

The mortuary in a community vet practice is a small refrigerated room (4 degrees Celsius for short-term storage of patients awaiting cremation collection) with its own dedicated exhaust at 10 ACH. The exhaust runs to atmosphere separate from the general HVAC. Cremation is almost always outsourced to a specialist contractor (pet aftercare services); the small number of practices with on-site cremation operate under EPA jurisdictional licensing and the cremator flue and abatement train are outside the HVAC scope.

Duct material is 316 stainless on mortuary and euthanasia extract because the chemical environment includes acidic decomposition products, formaldehyde from any incidental tissue fixation, and quaternary ammonium disinfectant for routine cleaning.

Sterilisation — AS 4187 in the veterinary context

AS 4187 was written for human-health settings but it is the accepted Australian benchmark for reprocessing reusable surgical instruments in any clinical environment, including veterinary. The standard sets out the workflow (dirty receive, manual clean, instrument inspection, packing, sterilisation, sterile storage, dispatch) and the environmental controls at each step.

The mechanical brief for a veterinary central sterilising department:

• Dirty receive and manual clean area at negative pressure (-10 to -15 Pa), 10 ACH, 22 degrees, NC-40, dedicated exhaust to atmosphere never recirculated. Duct material 316 stainless because of detergent and ultrasonic cleaning chemistry.
• Inspection and packing area at positive pressure (+10 Pa relative to dirty), 8 ACH, 21 to 22 degrees, RH 30 to 60 percent, NC-30. Duct material 304 stainless on extract, galvanised on supply.
• Steam steriliser (autoclave) bay with dedicated exhaust to atmosphere for steam vent, condensate trap on the discharge line, 10 ACH room ventilation. Duct material 316 stainless because of steam and chemistry.
• Sterile storage at positive pressure (+15 Pa relative to packing), 6 to 8 ACH, 18 to 22 degrees, RH 30 to 50 percent (low end critical to maintain sterile barrier integrity on packaged instruments), NC-35.

AVA Hospital of Excellence accreditation audits the AS 4187 workflow and ventilation cascade. Hospital tier audits the autoclave service records and the dirty-to-clean physical separation but is less prescriptive on the ventilation regime. Standard tier expects basic instrument reprocessing without a dedicated sterilising department.

Practice tiers — Standard, Hospital, Hospital of Excellence

The AVA Hospital Accreditation Scheme is a voluntary scheme but is the de facto industry benchmark. The tiers are useful as design briefs because they map directly onto the room program a designer must deliver.

• Standard. Community GP clinic with consult rooms, treatment, basic surgery, kennel and pharmacy. AVA Standard accreditation is the entry-level credential and is suitable for the typical suburban GP practice. Ventilation follows AS 1668.2 minimums for consult and treatment, with a basic surgical-suite air-change target of 6 to 8 ACH.
• Hospital. Adds a dedicated dental room, a fully-equipped surgical suite with anaesthetic gas scavenging, an isolation ward, a hospitalisation ward and a central sterilising department. Ventilation steps up to 8 to 12 ACH on surgical, mandatory pressure cascade through the central sterilising department, and dedicated cattery ventilation separate from canine.
• Hospital of Excellence. Specialty referral, emergency or teaching hospital with multiple specialty surgical suites, dedicated species wards (canine, feline, exotic, isolation), imaging suite (typically including CT and often MRI), oncology compounding suite and full AS 4187 reprocessing department. Ventilation is to ASHRAE Applications Handbook Chapter 9 throughout with HEPA H13 minimum on surgical supply, full pressure cascade, dedicated AHUs per species ward, dedicated extract risers for kennel, cattery and exotic, and full anaesthetic gas exposure measurement programme.

The mechanical engineer designing for any of the three tiers should brief the practice owner on which tier the design is targeting. Up-tiering after fit-out is expensive — the air-handling unit, the duct risers and the diffuser layout are difficult to retrofit. Down-tiering is wasteful. Setting the target tier at the start of design is the single highest-leverage decision in the project.

Australian veterinary practice landscape

The Australian small-animal veterinary market is consolidated at the top end and fragmented at the bottom. The fabricator serving the industry sees a mix of corporate-chain fit-outs, independent practice refits and specialty hospital expansions across the year. Knowing the players helps to position a fabricator's offering correctly.

Corporate consolidators. Greencross Vet Group is the largest, with more than 170 practices nationally, and is a sister business to the Petbarn retail chain. The Greencross corporate fit-out spec is consistent across new builds and refits, which means the duct fabricator who learns the Greencross brief wins repeat work. Vets All Natural Group operates a smaller chain with a wholistic-medicine positioning. PetSure Australia is the dominant pet-insurance underwriter and is occasionally cited in fit-out specifications because insurance-linked corporate clients flow through its preferred-practice network.

Specialty and referral hospitals. SASH (Small Animal Specialist Hospital) operates one of the largest specialty hospitals in Sydney and runs a referral-only model with full specialty teams (surgery, internal medicine, oncology, neurology, ophthalmology, cardiology, emergency and critical care, diagnostic imaging). The Animal Referral Hospital network operates the ARH brand in Homebush Sydney, Brisbane, Gold Coast and Sunshine Coast. Veterinary Specialists of Sydney operates referral hospitals in Ryde, Miranda and Botany. Sydney Animal Hospitals operates a network of full-service clinics linked to specialty referral. Royal Melbourne Veterinary Specialist Centre operates the Werribee specialty hospital. The Animal Hospital Murdoch is the WA-state benchmark for specialty referral and emergency care.

Emergency hospitals. Animal Emergency Service (AES) operates a network of after-hours and 24/7 hospitals across NSW and Queensland. Veterinary Emergency Group (VEG) is a US chain expanding into Australia with an open-floor-plan emergency model. Both operate 24/7 and demand more from the HVAC system than a GP clinic — continuous occupancy, continuous surgical workload, and a constant flow of anaesthetic gas exposure that must be controlled.

Charitable hospitals. Lort Smith Animal Hospital in Melbourne is the largest non-profit animal hospital in Australia and runs a full Hospital of Excellence specification under a charitable funding model. The Animal Welfare League and various RSPCA shelter clinics across the country operate smaller charitable practices with similar specification needs.

Single-clinic independents and regional practices. The long tail of the Australian veterinary market is small independent suburban practices (often a single owner-veterinarian plus a nurse and reception team, AVA Standard tier) and regional multi-vet practices such as Bell Veterinary Surgery in NSW that combine GP work with specialist services at AVA Hospital tier with a kennel block and a single surgical suite. The fabricator that delivers a clean, well-detailed galvanised duct package on time wins the next clinic referral.

University and teaching veterinary hospitals

The seven Australian university veterinary teaching hospitals are a distinct market segment — community-clinic patient flow with a research-and-teaching footprint. They combine the brief in this guide with the higher air-change rates and biocontainment compatibility described in our veterinary, animal research and laboratory animal HVAC guide. The teaching hospitals are: Sydney (Camden), Murdoch (The Animal Hospital Murdoch, WA), Melbourne (Werribee), UQ (Gatton), Charles Sturt (Wagga Wagga and Orange), Adelaide (Roseworthy) and JCU (Townsville). A duct fabricator quoting a university tender is quoting the union of both briefs.

Anaesthetic gas scavenging — design detail

Anaesthetic gas scavenging deserves a dedicated section because it is the single most-frequently mis-specified element in a veterinary fit-out, and the consequence of mis-specifying it is staff exposure measured in hundreds of ppm where the NIOSH limit is 2 ppm.

The system has four elements. The interface — typically an active-scavenging interface valve that connects to the anaesthetic machine's adjustable pressure-limiting valve outlet and presents a calibrated low-pressure regulator to the room. The transfer hose — a 30 mm conductive corrugated hose from the interface to the room wall. The scavenging duct — 316 stainless, hard-drawn copper, or PTFE-lined, sloped at 1:200 toward a moisture trap, sized for the connected anaesthetic machine population at 75 L/min nominal flow per machine. The active extract fan — a small dedicated fan at the roof termination, providing the negative pressure that pulls waste gas from each interface to atmosphere.

Termination is at atmosphere at least 7.5 m from any building intake and 3 m above the roof line per typical AS 1668.2 dispersion principles applied to point-source contaminants. The termination is fitted with a vermin-proof cowl, a moisture trap (because halogenated anaesthetic decomposition produces trace acidic condensate) and a flow-sensing alarm that signals to the nurses' station if the scavenging flow falls below the rated value.

Inspection: 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 in any duct section that is the wrong material specification.

Duct material decision matrix

Pulling the material specification together across the practice room program:

• Galvanised steel coil to AS/NZS 4254 (0.55 to 0.95 mm wall): reception, waiting, consult rooms, offices, staff rooms, pharmacy ambient, supply ducts in clinical rooms upstream of the room boundary (because supply air is filtered and not in contact with biological contamination). Cost-effective, widely supplied, fabricated on SBKJ SBAL-III auto duct line.
• Stainless 304 (0.55 to 1.2 mm wall): treatment and dental extract, recovery and ICU extract, kennel and cattery extract, exotic ward extract, surgical supply downstream of HEPA, sterile storage supply, compounding room general extract. Resistant to ammonia, quaternary ammonium disinfectant, citric-acid descaler. Fabricated on SBKJ SBAL-V stainless line or the SBAL-III with stainless coil module.
• Stainless 316 (0.55 to 1.5 mm wall): surgical extract, anaesthetic gas scavenging, mortuary and euthanasia extract, cytotoxic compounding extract, sterilisation steriliser exhaust, central sterilising department dirty-side extract. Resistant to halogenated anaesthetic decomposition products, formaldehyde, decomposition acids, autoclave steam chemistry. Fabricated on SBKJ SBAL-V stainless line.
• Hard-drawn copper or PTFE-lined: permitted alternative on anaesthetic gas scavenging in legacy refits where stainless tooling is not available; otherwise 316 stainless preferred.

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 consult, waiting, office and staff zones only — never in surgical, treatment, dental, recovery, ICU, kennel, cattery, exotic, sterilisation, mortuary 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:

• Consult rooms: NC-35. End-of-life consultations and consent conversations matter; diffuser whine matters.
• Surgical suite: NC-30. Surgical concentration. Phacoemulsifier and electrocautery pedals.
• Neurosurgical suite: NC-25. Intraoperative neurological monitoring sensitivity.
• Recovery and ICU: NC-30 to NC-35. Calm patients heal faster.
• Treatment and dental: NC-35.
• Pharmacy and dispensary: NC-35.
• Cattery: NC-35.
• Bird and exotic ward: NC-35.
• Boarding kennel: NC-40. Dog vocalisation noise floor dominates anyway.
• Reception and waiting: NC-35.
• CT scan room: NC-40. Scanner noise floor dominates.
• MRI scan room: NC-30 to NC-35, RF-isolated.
• Mortuary and euthanasia: NC-30.

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.

Why SBKJ machines are the correct line for veterinary fabrication

The veterinary duct fabricator delivers a mixed material brief: 70 to 80 percent galvanised by linear metre (for supply across the practice and for return in the non-clinical zones) and 20 to 30 percent stainless 304 and 316 (for extract on the clinical zones and for anaesthetic gas scavenging). The machine line that serves this brief efficiently has three elements.

• SBAL-III auto duct production line. Coil-fed, decoils through level-and-shear, notches and folds the duct blank, closes the Pittsburgh longitudinal seam and delivers a finished rectangular duct section in one pass. Configured for galvanised coil 0.5 to 1.2 mm with a stainless coil change-over module that supports 304 and 316 in the same wall-thickness range. Single-shift output 100 to 140 m of finished rectangular duct per shift.
• SBSF flanging line. Rolls TDF flange (transverse duct flange) and angle-flange terminations onto the duct end at 4 mm and 5 mm flange depths typical of veterinary supply and extract pressure classes. The TDF flange is the dominant connection in Australian veterinary fit-outs because it is faster on site than a hand-bolted angle, and the air-leakage rate at SMACNA seal class A is achievable with a properly-rolled TDF and a foam gasket.
• SBTF-1602 spiral tubeformer. Spiral-locks round duct from 100 mm to 1,600 mm diameter from galvanised or stainless coil. The 100 to 800 mm range covers virtually all round duct in a community veterinary fit-out (round duct is preferred for kennel, cattery and isolation extract because the spiral lock seam is more cleanable than a Pittsburgh seam on rectangular). The 800 to 1,600 mm range covers riser duct in larger specialty and emergency hospitals.

Optional add-ons that improve the fabricator's competitiveness on veterinary tenders: a TIG longitudinal seam-welding station on the SBAL-V for fully-welded stainless surgical extract; an automated insulation feeder for externally-insulated galvanised supply duct (saves 20 to 30 percent of the labour budget on a fit-out); a CNC plasma cutting station for stainless transitions, take-offs and irregular fittings.

The line accepts coil from local Australian steel merchants on either Pittsburgh seam (SBAL-III) or spiral lock (SBTF-1602), and produces ductwork to SMACNA seal class A, AS/NZS 4254 construction class A, and the leakage rates implied by AS 1668.2 ventilation regimes. The output is suitable for AVA Hospital and Hospital of Excellence tier facilities and for the corporate-chain specification used by Greencross, Animal Emergency Service, SASH and the Animal Referral Hospital network.

Commissioning a veterinary practice HVAC system

Commissioning is the closure step on every veterinary fit-out and the step on which AVA accreditation, state Veterinary Practitioners Board premises registration and the practice owner's confidence all depend. The commissioning protocol covers air change, pressure regime, temperature stability, anaesthetic gas 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 ±10 percent of design). Repeat the test annually.
• Pressure regime verification. Digital manometer at every door between zones of different pressure. Record the differential, the design target and the door state (open and closed). Repeat quarterly in surgical and sterile zones, annually elsewhere.
• Temperature and humidity stability. 7-day temperature and humidity log in every clinical room. Record the setpoint, the 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 halogenated anaesthetic and (if used) nitrous oxide concentrations against NIOSH limits. Repeat annually or after any anaesthetic machine change.
• Acoustic measurement. Sound-level meter at every clinical bench and operating table position. Record the NC level achieved against the 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. Repeat after any duct alteration.

The commissioning package — a bound report with all six 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 and the practice owner files with the lease. Skipping it costs the practice the accreditation and costs the fabricator the next referral.

How SBKJ supports veterinary HVAC fabricators

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

• Machine supply. SBAL-III auto duct line, SBSF flanging line, SBTF-1602 spiral tubeformer, with stainless-coil optionality where the fabricator's order book includes specialty hospital and emergency-hospital work. Standard 30/70 T/T commercial terms, CE marked, ISO 9001 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 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 strategic position SBKJ holds in the veterinary HVAC market is straightforward: we are the machine supplier that already knows the brief. Whether the project is a Greencross corporate roll-out, a 24/7 emergency hospital or a SASH-tier specialty referral, the duct fabricator on each project is running a SBAL-III or its equivalent — and we have already published the room-by-room reference (this guide) and know which seam type, coil specification and line setup produces the output efficiently.

Discuss your veterinary clinic duct line with an SBKJ engineer →

FAQ

What air change rate applies to a veterinary consult room?

AS 1668.2 sets the design rate at 10 L/s per person plus 0.6 L/s/m². In a typical 12 to 16 m² consult room with two to four occupants this delivers 6 to 8 air changes per hour. Temperature 22 to 23 degrees Celsius, RH 50 percent, NC-35 acoustic.

How is anaesthetic gas managed in a small-animal surgery?

Active scavenging at every anaesthetic machine, ducted through a 316 stainless or hard-drawn copper line to atmosphere at least 7.5 m from any intake and 3 m above the roof. NIOSH limits are 25 ppm nitrous oxide and 2 ppm halogenated anaesthetic; many practices target lower internal limits.

What pressure regime applies to a veterinary surgical suite?

+15 Pa relative to the corridor, 10 to 15 ACH, HEPA H13 supply filtration, 18 to 22 degrees Celsius. Recovery and ICU downstream operate at neutral to slightly negative pressure to prevent back-flow.

Should cat and dog wards share an air handling unit?

No. Best practice is a dedicated cattery AHU separate from canine boarding and ward. Cats are stressed by canine pheromones and feline upper-respiratory pathogens spread efficiently through shared ducts. Bird and exotic wards require a third dedicated AHU because of psittacosis biosecurity.

What ductwork material should be used in a veterinary clinic?

Galvanised to AS/NZS 4254 for general supply, reception and office. Stainless 304 for treatment, dental, recovery, ICU, kennel, cattery and exotic extract. Stainless 316 for surgical extract, anaesthetic gas scavenging, mortuary and cytotoxic compounding extract.

What Australian standards apply to a veterinary practice fit-out?

AS 1668.2 for ventilation, AS/NZS 4254 for duct construction, AS 4187 for sterilisation, AS 1668.1 for fire and smoke control, ASHRAE Applications Handbook Chapter 9 as design reference. AVA accreditation at Standard, Hospital or Hospital of Excellence tier. State Veterinary Practitioners Board for practitioner and premises licensing.

What SBKJ machines suit a veterinary clinic ductwork fabricator?

SBAL-III auto duct production line with galvanised plus 304 stainless coil capability, SBSF flanging line for TDF and angle terminations, SBTF-1602 spiral tubeformer for round runs up to 800 mm. Optional TIG seam welder for 316 stainless surgical and anaesthetic gas scavenging duct.