Veterinary Hospital, Animal Research and Laboratory Animal HVAC Duct Guide

Why animal facility ductwork is its own discipline

HVAC ductwork in animal facilities sits at the intersection of three normally separate disciplines: clinical hospital ventilation, biocontainment laboratory ventilation and food-grade corrosion engineering. None of those three handbooks alone gives a complete answer. A veterinary hospital that treats only the animal-as-patient question, missing the pheromone cross-contamination problem, ends up with a perfectly compliant operating theatre adjacent to a holding ward whose return air dumps cat allergen into the surgeon's lounge. A research vivarium that copies a pharmaceutical cleanroom design, missing the cage-wash corrosion question, finds 38 degree Celsius saturated steam pitting through galvanised return ductwork inside three years. A containment-rated facility that copies a microbiology PC3 lab, missing the species-density and ammonia load, has to rebuild the exhaust ductwork in 316L after the first AAALAC accreditation visit flags rust streaks behind the cage racks.

This guide consolidates the three disciplines into a single reference for HVAC engineers, sheet-metal fabricators and facility managers working on Australian veterinary hospitals, university vivariums, contract research organisation animal blocks and pharmaceutical company animal research suites. It is the same playbook the SBKJ engineering team uses when our customers in this sector — Greencross Vet Group hospital builds, Vetwest practice fitouts, Animal Referral Hospital sites, Lort Smith Animal Hospital in Melbourne, the Royal Melbourne Veterinary Specialist Centre, Murdoch University Veterinary Hospital, the University of Queensland Veterinary Medical Centre, the University of Adelaide veterinary precincts, and research vivariums for the Walter and Eliza Hall Institute, the Garvan Institute, Peter MacCallum Cancer Centre, QIMR Berghofer, Mater Research, Monash Biomedicine Discovery Institute, Telethon Kids Institute and CSL Behring vivarium operations — ask us what to specify, what to fabricate from, and what to commission against.

The guide is organised into ten parts. Part 1 frames the regulatory landscape. Part 2 covers air change rates. Part 3 covers pressure cascade. Part 4 covers outside air. Part 5 covers material selection. Part 6 covers HEPA filtration. Part 7 covers decontamination chemistry. Part 8 covers seam construction and fabrication. Part 9 covers commissioning and validation. Part 10 covers SBKJ machine configurations and supply.

Part 1 — Regulatory framework

Five documents govern almost every Australian animal facility design decision. Knowing which clause sits in which document is the difference between a smooth approval pathway and a six-month redesign loop.

ASHRAE Applications Handbook Chapter 16 — Laboratories

Chapter 16 of the ASHRAE Applications Handbook is the global engineering reference for laboratory ventilation including animal research facilities. It defines the once-through air strategy, the pressure cascade philosophy, recommended air change rates per room type, fume hood face velocity targets, and the conceptual structure of the supply, return and exhaust system. Chapter 16 is referenced by AS/NZS 2243.3:2022 and by AAALAC International. Most consulting engineers in Australia who specify vivarium HVAC start every project with a copy of Chapter 16 open on the desk.

ASHRAE Applications Handbook Chapter 23 — Health Care

Chapter 23 covers health care facilities including veterinary hospitals. It supplies the hospital-grade air change rates, surgery suite positive-pressure rules, isolation room negative-pressure rules and the airflow direction logic that veterinary hospitals adopt by analogy with human hospitals. Chapter 23 also informs the medical gas, anaesthesia gas scavenging and humidity control sections that veterinary surgical suites borrow directly from human OR design.

AS/NZS 2243.3:2022 — Safety in laboratories: Microbiological safety and containment

AS/NZS 2243.3:2022 is the Australian and New Zealand standard for biological containment in laboratories and animal research facilities. It defines the four physical containment levels — PC1 through PC4 — and prescribes the engineering controls each level requires. The 2022 revision tightened HEPA filter validation requirements, refined the bag-in-bag-out specification, mandated improved decontamination protocols and aligned the pressure cascade and airlock design with the World Health Organization Laboratory Biosafety Manual. Any animal research facility handling regulated biological material in Australia or New Zealand certifies against AS/NZS 2243.3:2022.

NHMRC Australian code for the care and use of animals for scientific purposes (8th edition)

The National Health and Medical Research Council code is the welfare and ethics code that governs all animal research in Australia. It is referenced by every state Animal Welfare Act and is enforced by Animal Ethics Committees at every research institution. While the code is primarily a welfare and oversight document, it carries explicit ventilation expectations: minimum air change rates, ammonia limits, temperature and humidity ranges per species, and noise control requirements. Engineers cannot avoid the NHMRC code because every Animal Ethics Committee approval references it and every facility design proposal is reviewed against it.

AAALAC International accreditation

AAALAC International is the global accreditation body for animal research programmes. Australian institutions seeking AAALAC accreditation — most major universities, several CRO and pharmaceutical animal blocks — have to satisfy AAALAC site visit assessors who use the Guide for the Care and Use of Laboratory Animals (the United States National Research Council Guide) as the primary technical reference. The Guide and AAALAC site visits emphasise air quality, environmental enrichment, pressure cascade integrity, HEPA filter integrity and the chain of custody for decontaminated waste streams. An AAALAC site visit will absolutely lift a ceiling tile to check duct condition, hold a vaneometer at the diffuser, and ask the facility manager when HEPA filters were last challenge-tested.

Other reference documents

Secondary references in routine use include AS 1668.2 for ventilation in buildings (the supply and exhaust air rates baseline), AS 4260 for HEPA filter classification, ISO 14644 series for cleanroom and clean zone classification, the Therapeutic Goods Administration manufacturing principles where animals produce regulated biologics, and AS/NZS 4254 for ductwork construction. The full suite is the toolbox; the engineering judgement is in selecting which clause governs a specific room.

Part 2 — Air change rates

Air change rates are the most-debated and most-misapplied single number in animal facility HVAC. The headline numbers are well known. The judgement is in which number applies where.

General animal holding rooms — 10 to 15 ACH

For routine rodent, rabbit, ferret and small species holding rooms, ASHRAE Chapter 16 and the Guide for the Care and Use of Laboratory Animals recommend 10 to 15 air changes per hour. The lower bound applies where ventilated cage racks remove most of the cage-level heat and ammonia load and the room ventilation is principally a macro-environmental conditioner. The upper bound applies where static cages or open cages dominate and the room itself has to handle ammonia, allergen and heat removal. The choice of rack type determines where on the 10 to 15 range a project lands.

Procedure and operating rooms — 15 to 20 ACH

Procedure rooms and animal operating theatres typically operate at 15 to 20 ACH, mirroring the general OR rate from ASHRAE Chapter 23. Surgical suites adopt positive pressure and the higher ACH end to manage anaesthetic gas, surgical smoke and the heat load from surgical lighting. Anaesthetic gas scavenging is a separate dedicated exhaust, not a function of the room ventilation system, and is sized independently per AS 2896 medical gas pipeline rules where applicable.

High-load species — 20 to 25 ACH

Non-human primate, dog, swine and high-density rodent rooms run at 20 to 25 ACH. The driver is the per-animal heat and metabolic load: a 30 kg primate puts out roughly 60 watts continuously and ammonia from urine accumulates rapidly. Dog wards and primate rooms also have higher acoustic loads from vocalisation; the higher ACH supports pressure cascade integrity even when doors open frequently for access. Smaller institutions sometimes try to operate primate rooms at 15 ACH on cost grounds; AAALAC site visit assessors flag this within an hour of arrival.

Cage wash — 15 ACH minimum, 100 percent outside air

Cage wash and cage processing areas operate at 15 ACH minimum with 100 percent outside air, dedicated steam-rated exhaust and no recirculation. The exhaust handles 38 degrees Celsius water vapour at 100 percent relative humidity carrying detergent and disinfectant aerosols. Recirculating cage-wash exhaust into any other zone is a hard prohibition.

Necropsy — 15 ACH minimum, downdraft tables, no recirculation

Necropsy rooms operate at 15 ACH minimum but the design driver is rarely the room ACH. The driver is the downdraft table exhaust capture velocity, typically 0.5 m/s at the table surface, and the formaldehyde Time Weighted Average target. The room ACH supports background dilution; the downdraft table exhaust carries the formaldehyde and the bioaerosol load to atmosphere through HEPA and activated carbon polishing.

Surgical recovery and isolation

Surgical recovery rooms operate at 15 ACH and follow the species-appropriate temperature range. Veterinary isolation wards holding animals with suspected infectious disease operate at 12 to 15 ACH at negative pressure with anteroom airlock. The pressure differential — typically minus 15 Pa relative to corridor — is more important than the absolute ACH for veterinary isolation.

Part 3 — Pressure cascade

Pressure cascade is the macro-engineering control that prevents cross-contamination between species, between dirty and clean operations and between contained agents and the corridor. Designed correctly, the cascade survives door openings, fan trips and stocking changes. Designed badly, the cascade collapses the first time a procedure room door is held open by an animal-carrier trolley.

The standard cascade

A typical Australian vivarium cascade runs:

• Clean change rooms and gowning at +15 to +25 Pa relative to corridor.
• Corridor at 0 Pa (the reference datum).
• Animal holding rooms at -15 to -25 Pa.
• Cage wash dirty side at -15 to -25 Pa.
• Necropsy and post-mortem at -30 Pa.
• Quarantine and infectious holding at -30 Pa with anteroom at -15 Pa.

The reference is always the corridor. Every door crossed by an operator should produce a clear felt and visible airflow direction from clean to dirty, never the reverse. Smoke pencils on commissioning day visualise this for the AAALAC site visit photograph.

Anterooms and airlocks

PC3 holding rooms, primate quarantine and any zone above PC2 require an anteroom or airlock. The anteroom sits at intermediate pressure between the corridor and the inner room. Designed correctly, the anteroom buffers the cascade against simultaneous door operation. PC4 facilities take this further with a fully sealed envelope, double-door airlocks with mechanical interlocks preventing simultaneous opening, and full HEPA filtration on both supply and return air streams.

Pressure measurement and indication

Every cascade-managed door has a wall-mounted differential pressure gauge or a digital Magnehelic-equivalent display showing the differential to corridor. Visual confirmation at the door is the operational check; logged building management system trends provide the audit record. Some institutions install audible alarms triggered by cascade collapse; others rely on facility-management-system alerts to the animal facility manager's mobile phone. AAALAC site visits expect at least one of these.

Maintaining cascade under door opening

Door opening events temporarily collapse the cascade. The HVAC system response — variable air volume box reaction, exhaust track-and-trim algorithm, fan response — has to be tuned to ride through a 5 to 10 second door opening without losing absolute pressure direction. Modern variable-air-volume controls with fast-response venturi valves achieve this; older constant-volume systems with simple offset relays do not, and the cascade reverses for several seconds every door cycle.

Part 4 — Outside air strategy

The single most consequential decision in animal facility ventilation is the outside air ratio. The Guide for the Care and Use of Laboratory Animals, the NHMRC code and AS/NZS 2243.3:2022 all converge on the same answer for animal holding rooms: 100 percent outside air, no recirculation between rooms.

The reasoning is straightforward. Animal holding rooms generate species-specific allergens and pheromones. Mixing exhaust air from a mouse holding room with supply air destined for a rabbit holding room sensitises the rabbits' immune systems to mouse allergen, and vice versa. Mixing exhaust air from a primate room with any return-air loop in the same building exposes facility-management staff to primate allergen at nuisance levels. Mixing exhaust air from a dog ward with anywhere on a return-air loop produces the kind of complaint that ends with a facility manager rebuilding the air handling unit.

The energy penalty for 100 percent outside air is significant — Melbourne winter conditions require heating from 4 degrees Celsius to a 22 degree Celsius supply set-point on a 100 percent outside air system, and Brisbane summer conditions require cooling and dehumidification from 32 degrees Celsius and 80 percent relative humidity. Heat-recovery wheels, run-around coils and plate heat exchangers recover 50 to 70 percent of this energy without any return-air mixing — the recovery happens between the exhaust and supply air streams without any mass transfer. This is the standard Australian design approach for vivariums of any reasonable scale.

The exception to the 100 percent outside air rule is in certain highly-engineered closed-rack systems where the rack itself is a mini barrier and the room serves as a less critical macro-environment. Even then, the room exhaust is once-through to atmosphere, never recirculated to other rooms.

Part 5 — Material selection

The single most expensive line item in animal facility ductwork failures is corrosion. Galvanised steel does not survive an animal facility operational environment for the design life of the building. The choice of material is settled at concept design and never revisited cheaply.

Why galvanised steel fails

Galvanised steel ductwork fails in three predictable ways inside an animal facility:

• Ammonia attack. Urine breakdown produces ammonia. In the presence of moisture, ammonia and zinc react to form zinc-ammine complexes that are water-soluble. The galvanised coating is consumed within 12 to 24 months in any duct downstream of cage banks. Once the coating is gone, the underlying carbon steel rusts rapidly under animal-facility humidity.
• Decontamination chemistry. Vaporised hydrogen peroxide cycles, chlorine dioxide cycles and formaldehyde gas cycles all attack zinc. A single VHP cycle at 1,000 ppm for 90 minutes strips visible zinc from any galvanised duct internal surface. Decontamination is a periodic, planned event — galvanised cannot survive it.
• Cage wash exhaust. 38 degree Celsius steam at 100 percent relative humidity carrying detergent and chlorinated disinfectant aerosols pits galvanised within months. White rust appears at every spot weld and seam. Within five years, the duct interior is brown rust running into condensate at the low points, dripping at every transition.

304 stainless — the minimum standard

304 stainless steel is the minimum specification for animal holding exhaust, cage-wash supply, and clean corridor supply ductwork. 304 handles ammonia exposure indefinitely. It survives most decontamination cycles. It is weldable, formable, polishable and cost-competitive against other corrosion-resistant alternatives. The cost premium over galvanised is roughly 2.5 to 3 times raw material cost, offset by 30+ year service life with zero coating maintenance.

316L stainless — the high-decon specification

316L stainless adds molybdenum to the alloy, conferring resistance to chloride attack and to oxidising-acid environments. 316L is mandatory for cage-wash exhaust where chlorinated disinfectant aerosols concentrate, for necropsy exhaust where formaldehyde produces methanol-rich condensate, for decontamination plenums where chlorine dioxide and vaporised hydrogen peroxide concentrate, and for any duct exposed to seawater or salt-laden atmosphere on coastal sites. 316L costs roughly 30 to 50 percent more than 304 in coil form; the upgrade is decided per duct run, not blanket-applied.

The "L" in 316L

The L denotes low-carbon — typically 0.03 percent carbon maximum versus 0.08 percent for standard 316. Low carbon prevents chromium-carbide precipitation at grain boundaries during welding (sensitisation) which would otherwise leave a corrosion-vulnerable heat-affected zone alongside every weld bead. For ductwork that will be welded — and biocontainment ductwork is welded — 316L is the standard, not 316.

Surface finish

Internal surface finish matters for both biosafety and decontamination. A 2B mill finish (cold-rolled, annealed, pickled) is acceptable for most animal facility applications. Where chlorine dioxide or vaporised hydrogen peroxide decontamination is routine, a #4 brushed or 2B-with-passivation finish reduces particle adhesion and accelerates decon penetration. PC4 facilities sometimes specify electropolished internal surfaces; this is rare in animal facilities outside the highest-containment research applications.

Alternative materials

Aluminium is occasionally specified for cage-wash exhaust where the chloride load is moderate and weight matters; it is rarely a good answer because aluminium reacts with strong alkaline detergents. Fibreglass-reinforced plastic ductwork survives corrosive exhaust well but does not handle the 38 degree Celsius steam plus mechanical load combination cleanly and is rarely allowed in PC3 and PC4 envelopes because of decontamination chemistry compatibility concerns. PVC and PVC-coated steel are not acceptable in any animal-facility duct application. The realistic palette is 304 stainless, 316L stainless, occasionally aluminium for non-critical duct runs, and absolutely never galvanised inside the contamination envelope.

Part 6 — HEPA filtration

HEPA filtration is the engineered barrier between the animal facility and the outside world for biological agents. Filter selection, housing design and validation procedure are tightly interlinked.

HEPA H14 — the standard

AS/NZS 2243.3:2022 specifies HEPA filters meeting EN 1822 H14 classification: greater than 99.995 percent efficiency at the most penetrating particle size (typically around 0.2 to 0.3 micrometres). H13 is the older standard at 99.95 percent efficiency; H14 is now the convention for new Australian PC3 and PC4 facilities. Where the agent risk class warrants, H15 ULPA filtration is specified (greater than 99.9995 percent efficiency at MPPS); this is rare outside dedicated PC4 research.

What gets HEPA filtration where

• PC1 and PC2 holding rooms. No HEPA filtration on supply or exhaust to atmosphere. HEPA on biological safety cabinet exhaust within the room.
• PC2 with infectious agents. HEPA on exhaust from biological safety cabinets and from any room with active infectious agent work.
• PC3 holding rooms. HEPA H14 on the room exhaust before any downstream equipment, in bag-in-bag-out housings.
• PC4 holding rooms. Redundant HEPA H14 on both supply and exhaust, in bag-in-bag-out housings with isolation dampers, and challenge-test ports for in-situ DOP or PAO testing.
• Necropsy exhaust. HEPA H14 followed by activated carbon polishing for formaldehyde and bioaerosol management.
• Cage wash exhaust. Pre-filter for lint and detergent aerosol; HEPA filtration is rare unless cage washing handles infectious cages.

Bag-in-bag-out housings

Bag-in-bag-out (BIBO) housings allow filter change without exposing the maintenance technician to the upstream contaminated air. The filter is sealed inside a continuous PVC bag during change-out; the new filter is bagged in via the same continuous bag system; the old filter is bagged out. BIBO housings are mandatory for any HEPA bank that may be exposed to infectious aerosols — that is, any PC3 or PC4 exhaust HEPA, plus any biological safety cabinet exhaust HEPA carrying suspected infectious work. BIBO housing design is covered by AS 4260 and ISO 14644-7.

In-situ challenge testing

HEPA filters in containment service are tested in situ rather than relying on factory test certificates alone. The standard test is an aerosol challenge using DOP (di-octyl phthalate) or, more commonly today, PAO (polyalpha-olefin) injected upstream of the filter and measured downstream with a photometer. The acceptance criterion is leakage less than 0.01 percent of upstream challenge concentration. Annual or six-monthly challenge testing is the operational standard. The duct upstream and downstream of the filter requires test ports — typically 25 mm sample ports with sealed plugs — at the supplier's specified locations.

Pre-filtration

HEPA filters are protected by upstream pre-filters: typically a G4 pre-filter and an F8 or F9 secondary. The pre-filters extend HEPA service life from 12 months to 3 to 5 years in clean service. Pre-filter housings are far simpler than HEPA housings and are routinely fabricated from 304 stainless even where downstream HEPA housings are 316L.

Part 7 — Decontamination chemistry

Decontamination is the periodic chemical sterilisation of the animal facility envelope. It is required between species changeovers, after suspected infectious incidents, before any HEPA filter change in containment service, and as scheduled preventive practice in PC3 and PC4. Three chemistries dominate.

Vaporised hydrogen peroxide (VHP)

VHP is the modern standard for room and ductwork decontamination. A typical cycle injects hydrogen peroxide vapour at 250 to 1,000 ppm into a sealed envelope for 60 to 90 minutes, achieving a 6-log reduction of bacterial spores. VHP residue is water and oxygen — there is no toxic by-product to manage. VHP attacks zinc aggressively (hence galvanised ductwork failure) but is compatible with stainless steel, EPDM gaskets and standard biocontainment materials. VHP requires the envelope to be sealed during the cycle and ventilated on cycle completion to drop residual concentration below 1 ppm before re-entry.

Chlorine dioxide gas (ClO2)

ClO2 gas is an older but still-used decontamination chemistry. ClO2 is generated on site from sodium chlorite and hydrochloric acid, injected into the envelope at 1 to 2 mg/L for 1 to 2 hours, then ventilated. ClO2 is highly effective against spores and viruses but more aggressive on materials than VHP — including on natural rubber gaskets, on aluminium and on galvanised. 316L stainless tolerates ClO2 cycles indefinitely; 304 stainless is acceptable for occasional ClO2 cycles but is not the preferred specification where ClO2 is routine.

Formaldehyde gas

Formaldehyde gas decontamination is the legacy chemistry, still used in some institutions because of historical capability and validated efficacy. A typical cycle vaporises paraformaldehyde at the rate of 10 to 20 g/m³ in a sealed envelope, holds for 6 to 8 hours at 70 to 80 percent relative humidity, and then neutralises with ammonia gas to convert formaldehyde to non-toxic hexamethylenetetramine. Formaldehyde is a known human carcinogen, generates regulatory paperwork, and is being progressively replaced by VHP for new facility builds. Where formaldehyde is in use, all envelope ductwork must be 316L because of the methanol-rich condensate produced during the cycle.

Chemical compatibility

The duct and gasket material specification has to match the planned and the foreseeable decontamination chemistries. A facility that specifies VHP only at design stage and later adds chlorine dioxide capability finds the EPDM gaskets fail. A facility that uses 304 stainless throughout and later switches to weekly ClO2 cycles finds the heat-affected zones beside each weld pit through within five years. The honest answer at design stage is: specify 316L stainless with ETP or PTFE gaskets in the entire decontamination envelope, regardless of which chemistry the operations team plans to use today.

Necropsy formaldehyde — workplace exposure

Necropsy rooms generate formaldehyde during tissue fixation. Australian Workplace Exposure Standards set Time Weighted Average at 1 ppm and Short Term Exposure Limit at 2 ppm. Many institutions adopt a more conservative 0.75 ppm Occupational Exposure Limit on the basis of recent epidemiological evidence. Engineering controls — downdraft tables, local exhaust ventilation, dedicated exhaust ductwork in 316L stainless, HEPA and activated carbon polishing of the exhaust before discharge to atmosphere — are the primary control hierarchy. Personal protective equipment is the last line. Air monitoring during fixation activities documents compliance for the workplace health and safety record.

Part 8 — Seam construction and fabrication

Seam construction determines whether a duct survives its decontamination cycles, holds its pressure cascade and passes its leak test. The choice of seam type is driven by containment level, not by sheet-metal-shop preference.

PC1 and general veterinary — Pittsburgh seam, sealed

For PC1-equivalent veterinary holding, surgical recovery and general procedure rooms, a standard Pittsburgh lock seam closed with biosafety-grade sealant is acceptable. The Pittsburgh seam is mechanically interlocked with low leakage rates when sealed. Sealant choice matters — silicone-based duct sealant is fine for general HVAC; for animal facility duty the sealant must be water-resistant, fungicidal, and compatible with the planned cleaning chemistry.

PC2 and high-load veterinary — Pittsburgh with continuous welded reinforcement

PC2 holding rooms and high-density veterinary surgical suites typically tighten the construction to Pittsburgh seams with continuous welded reinforcement at every transverse joint. The longitudinal Pittsburgh is sealed; the transverse joints are TIG-welded. This combination achieves leak rates below 1 percent of system volume at design pressure — the standard for PC2 service.

PC3 — fully welded longitudinal and circumferential

PC3 ductwork inside the contamination envelope is fully welded — every longitudinal seam, every transverse joint. The TIG (gas tungsten arc) process is the standard for stainless duct welding because it produces clean, low-spatter, fully-penetrating welds without filler-metal contamination. Argon shielding gas, low heat input, post-weld passivation with citric or nitric acid pickle paste, and final visual inspection produce welds that match the parent metal in corrosion resistance.

PC4 — fully welded with pressure-decay testing

PC4 ductwork is fully welded as for PC3, plus pressure-decay tested seam by seam. The acceptance criterion is leak rate below 0.05 percent of system volume — an order of magnitude tighter than PC3. Pressure-decay testing isolates a duct section, pressurises to design pressure plus 50 percent test margin, and measures decay over a 30 minute test period. The inspection regime is documented seam-by-seam and held in the facility commissioning records for the AAALAC site visit and the regulatory submission.

Spiral round versus rectangular

Spiral round ductwork is preferred over rectangular for animal facility service for four reasons. First, fewer corners means less harbourage for biological contamination and less surface area for ammonia residue. Second, the continuous spiral seam is straightforward to weld for biocontainment service. Third, pressure-loss is roughly 20 percent lower than equivalent rectangular ductwork, reducing fan power and the noise transmitted into noise-sensitive holding rooms. Fourth, decontamination penetrates whole-bore more uniformly in round ductwork than in rectangular with internal stiffeners and TDF flange protrusions.

Rectangular ductwork survives where coordination, ceiling-void depth or low-velocity diffuser plenum requirements demand it. Where rectangular is selected for PC2 and above, TDF flanges are not used inside the contamination envelope — TDF creates internal bead protrusions that trap residue. Companion-angle flanges with continuous gasket and full TIG weld at the corners are the alternative for rectangular-in-containment service.

Welding processes

For 304 and 316L stainless duct fabrication the welding process choices are TIG (GTAW), MIG (GMAW), pulsed-MIG and laser welding. TIG dominates for biocontainment ductwork because it produces clean, low-spatter welds without filler metal contamination of the duct interior. Pulsed MIG with stainless wire and argon-helium-CO2 shielding gas is acceptable for less critical ductwork where production speed matters more than weld bead aesthetics. Laser welding produces very clean welds but capital cost rules it out for most fabrication shops. Stick (SMAW) welding is not used for thin-section duct; the heat input pits the parent metal.

Part 9 — Commissioning and validation

Commissioning is the structured handover from construction to operation. For animal facilities the commissioning plan has to satisfy three audiences: the building services consultant signing off mechanical performance, the Animal Ethics Committee accepting the facility for stocking, and the AAALAC site visit assessor checking the facility against the Guide.

Pre-commissioning

Pre-commissioning verifies the construction matches the design: duct material, gauge, seam type, hanger spacing, gasket material. A pre-commissioning walk-through with the consulting engineer signs off the as-built before the testing-and-balancing contractor starts.

Testing and balancing (TAB)

TAB measures and adjusts air volume at every supply diffuser and every exhaust grille, and confirms the room ACH against the design intent. Pressure cascade is measured between every cascade-managed door, including with adjacent doors held open and closed in combination to test cascade resilience. The TAB report is signed against the design schedule and forms the operational baseline for future re-balancing.

HEPA in-situ challenge

Every HEPA filter in containment service is challenged in situ post-installation and before commissioning sign-off. DOP or PAO is injected upstream; a photometer measures downstream concentration; leak rate is logged for each filter and signed off by the testing technician. Challenge testing is repeated annually or semi-annually thereafter.

Smoke visualisation

Smoke pencils visualise airflow patterns at supply diffusers, return grilles and door openings. The objective is to confirm the design airflow direction at every cascade boundary, photograph it, and document any unexpected flow patterns for engineering review. Smoke visualisation at door openings is the most informative single test for cascade integrity. AAALAC site visit assessors will repeat smoke visualisation during their visit.

Stocking trial

Before live stocking, many facilities run a stocking trial: design-density cage racks installed and powered, ventilated cage rack airflows turned on, all HVAC running under design occupancy load. This confirms the room and rack airflows work together and identifies any local pressure or flow anomalies before live animals arrive. A stocking trial finds problems that paper analysis misses.

Operational handover

The handover package includes: TAB report, HEPA challenge test reports, smoke visualisation video and photographs, decontamination cycle validation report, operations and maintenance manual with system schematics, spare parts list, and a year-one preventive maintenance schedule. The animal facility manager owns the package thereafter.

Part 10 — SBKJ machine configurations for stainless animal facility ductwork

SBKJ is a manufacturer of HVAC ductwork production machinery. Our customers fabricating ductwork for veterinary, vivarium and PC2/PC3 facilities specify three machines as the core supply, plus a fourth for fully-welded biocontainment work.

SBAL-V stainless auto duct line

The SBAL-V is the SBKJ rectangular auto duct line configured for stainless steel coil. Standard configuration handles 304 and 316L stainless coil from 0.6 mm to 1.6 mm wall thickness, coil width up to 1,550 mm, output rated for single-shift production of rectangular ductwork to AS/NZS 4254 and EN 1505 tolerances. The SBAL-V integrates a TIG welding station for Pittsburgh seam closure on critical ductwork — the alternative to mechanical seam-and-sealant for PC2 and above. The PLC is Siemens or Mitsubishi (open architecture, source code accessible to the operator), the HMI is a 15-inch colour touch screen with multilingual operator interface, and the safety interlock layer meets CE Machinery Directive 2006/42/EC.

SBTF-1602 spiral tubeformer

The SBTF-1602 is the SBKJ spiral tubeformer rated for round duct from 80 mm to 1,600 mm diameter in stainless coil up to 1.5 mm wall thickness. The spiral seam is lock-formed at production speeds up to 30 m/min. For biocontainment service, the spiral seam is then welded by a separate TIG seam welder running along the spiral path. The SBTF-1602 is the preferred SBKJ machine for animal facility round ductwork — fewer corners, lower harbourage, easier whole-bore decontamination.

TIG longitudinal seam welder

The SBKJ TIG longitudinal seam welder is configured for longitudinal welding of round and rectangular stainless duct seams. Argon shielding, programmable current and travel speed, automatic arc-length control and continuous-wire feed for filler metal where required. The output is a fully-penetrated, low-spatter, post-weld pickle-passivated seam suitable for PC3 service. SBKJ supplies the TIG welder bundled with the SBTF spiral tubeformer for biocontainment-grade spiral round duct or as a stand-alone station for fabricators welding seams produced on other forming equipment.

Auxiliary equipment

SBKJ supplies a complete auxiliary equipment package for stainless animal-facility ductwork fabrication: stainless slitter for coil-to-coil width conversion, stainless decoiler with weight capacity matched to the SBAL-V or SBTF-1602, stainless-compatible coiling cradle, plasma cutting station for stainless plate up to 6 mm, and a passivation rinse bay for post-weld pickle treatment. Every machine is CE marked and ISO 9001:2015 quality system manufactured.

Australian site supply

SBKJ Group operates from Box Hill North VIC and supplies machines, spare parts and commissioning support to Australian animal-facility ductwork fabricators directly. Our installed base in Australian institutions includes auto duct lines and spiral tubeformers in service supplying ductwork to teaching hospitals, university vivariums and pharmaceutical research animal blocks. Lead time from order to commissioned-on-site for the SBAL-V stainless line is typically 14 to 16 weeks; the SBTF-1602 with TIG welder is 12 to 14 weeks. We support 30/70 T/T payment terms and never request 100 percent prepayment. Spare parts continuity is guaranteed in writing for at least ten years from machine commissioning.

Worked example — Australian university vivarium

To put the principles into a single picture, consider a generic Australian university research vivarium project: 1,200 m² gross floor area, mixed PC2 and PC3 zones, 18 holding rooms, 4 procedure rooms, 2 surgical suites, 1 cage wash, 1 necropsy, 2 quarantine rooms with anteroom, single-storey, on a metropolitan teaching campus. The HVAC ductwork specification would resolve as follows.

Air change rates

General mouse and rat holding rooms run at 12 ACH on ventilated cage racks; rabbit and ferret holding at 15 ACH; primate quarantine at 22 ACH; procedure rooms at 18 ACH; surgical suites at 20 ACH at positive pressure; cage wash at 15 ACH dirty side and 12 ACH clean side, both 100 percent outside air; necropsy at 15 ACH room background plus downdraft table at 0.5 m/s capture velocity.

Pressure cascade

Clean change rooms at +20 Pa; corridor at 0 Pa datum; holding rooms at -20 Pa; quarantine rooms at -30 Pa with anteroom at -15 Pa; surgical suites at +15 Pa relative to corridor; necropsy at -30 Pa; cage wash dirty side at -20 Pa, clean side at +10 Pa.

Outside air strategy

100 percent outside air through three rooftop air handling units sized for total facility supply load. Heat recovery via run-around coil between exhaust and supply with 60 percent sensible recovery. No return-air mixing between rooms. Total exhaust through nine roof-mounted exhaust fans grouped by zone class — PC2 holding bank, PC3 holding bank, surgery bank, cage wash bank, necropsy bank, primate quarantine bank — with HEPA filtration on the PC3 holding bank, primate quarantine bank and necropsy bank exhausts.

Material selection

304 stainless for all supply ductwork inside the contamination envelope; 304 for general holding-room exhaust within the envelope; 316L for cage-wash exhaust, necropsy exhaust, primate quarantine exhaust, the entire PC3 holding zone, and all exhaust ductwork between the HEPA bank and the discharge point on the roof; galvanised acceptable for the outside-air intake plenum upstream of the supply HEPA filters and the heat-recovery coil; galvanised acceptable for the corridor return air (corridor return is permitted because the corridor is the cleanest zone and recirculation is to its own supply only). The supply air to PC3 holding rooms goes through a HEPA bank at the room boundary, mounted in a 316L plenum inside the room.

HEPA filtration

HEPA H14 on supply to surgical suites and PC3 holding rooms; HEPA H14 on exhaust from PC3 holding, primate quarantine, necropsy and biological safety cabinets in PC2 procedure rooms; bag-in-bag-out housings for all HEPA banks on potentially contaminated exhaust; pre-filtration G4 plus F8 protecting every HEPA bank.

Seam construction

Pittsburgh sealed seams for general HVAC outside the contamination envelope; Pittsburgh sealed plus TIG-welded transverse joints for PC2 holding rooms; fully welded longitudinal and circumferential for PC3 holding, primate quarantine, necropsy exhaust and cage wash exhaust. Spiral round ductwork preferred wherever ceiling-void geometry allows; rectangular only for the surgical suite ceiling plenums where coordination demands it.

Decontamination plan

VHP capability across the entire envelope. ClO2 capability for primate quarantine and PC3 holding. Formaldehyde retained only for legacy biological safety cabinet decontamination during decommissioning. EPDM gaskets throughout, with PTFE upgrades on the ClO2 zones. Annual VHP decontamination of cage wash; quarterly VHP decontamination of holding rooms during species changeover; pre-stocking VHP cycle on every newly stocked room.

Fabrication machinery

Project ductwork is fabricated by a Melbourne-based stainless duct contractor running an SBKJ SBAL-V auto duct line for rectangular sections and an SBKJ SBTF-1602 spiral tubeformer for round sections, with a TIG longitudinal seam welder running each spiral seam intended for PC3 service. The fabrication shop runs the rectangular and round lines in parallel, scheduling fully-welded sections for the PC3 banks and Pittsburgh-sealed sections for PC2 and below.

Commissioning

TAB by an independent contractor; HEPA in-situ DOP challenge by the HEPA supplier's certified technician; smoke visualisation at every cascade boundary photographed for the operations and maintenance manual; pressure cascade verified in 12 door-state combinations per zone; full stocking trial run for two weeks before live animal arrival; AAALAC site visit pre-audit with internal animal facility committee one month before the formal site visit.

Common failure modes and how to avoid them

The same handful of failure modes recur across animal-facility HVAC retrofits. Designing them out at concept stage is cheaper than fixing them on year three.

• Galvanised exhaust pitting at year three. Caused by specifying galvanised inside the contamination envelope to save capital cost. Solved by specifying 304 stainless minimum from concept design.
• Cascade collapse on door opening. Caused by slow-response constant-volume control. Solved by variable-air-volume venturi valves with millisecond response time and a control-system tuning round at commissioning.
• HEPA filter wet-out in cage wash exhaust. Caused by saturated steam reaching the filter face. Solved by an upstream demister or coalescer, plus heat trace on the duct between the cage wash and the HEPA bank.
• Formaldehyde exposure breach in necropsy. Caused by inadequate downdraft table capture velocity at the table edges. Solved by table-edge baffles, dedicated 316L exhaust ductwork with no recirculation, and air-monitoring during fixation procedures.
• Allergen cross-contamination between species. Caused by return-air mixing at the air handling unit. Solved by 100 percent outside air strategy with sensible heat recovery and zero mass transfer between exhaust and supply streams.
• Decontamination cycle failure due to envelope leak. Caused by insufficient seam-welding or by gasket degradation. Solved by pressure-decay testing every PC3 envelope post-installation and at five-year intervals thereafter.
• Noise above NC 50 in primate rooms. Caused by porous internal duct lining absorbing decontaminant and shedding fibre. Solved by external lagging only, plus pre-insulated double-wall stainless plenum boxes upstream of diffusers.
• Sensitisation of facility staff to species allergen. Caused by cumulative exposure in corridors with mixed return-air systems. Solved by once-through corridor ventilation, gowning protocols and personal protective equipment requirements at the door of every high-allergen zone.

Operational considerations

HVAC ductwork is the long-life capital element of an animal facility. The design choices made at concept stage are still in service 30 years later when the facility is on its third species programme and its fifth animal facility manager. A few operational considerations worth flagging at design stage:

• Provide access panels at every change of direction and at every HEPA housing for inspection and cleaning. Animal-facility ductwork accumulates ammonia residue and dust on the lower surfaces of horizontal ducts; access panels at each transition allow inspection and cleaning without major shutdown.
• Label ductwork at every accessible point with zone, service and direction-of-flow. AAALAC site visit assessors check labelling. Maintenance technicians during emergency response work faster with clear labelling.
• Hard-pipe condensate drains from cage-wash exhaust ductwork directly to a tundish drain. Do not allow condensate to accumulate at low points. Slope all cage-wash exhaust ductwork at 1 in 100 minimum towards drains.
• Provide reasonable redundancy on critical exhaust fans. PC3 and PC4 facilities require N+1 fan redundancy as a regulatory requirement; many sites apply N+1 to PC2 holding-room exhaust as good practice.
• Schedule a five-year mid-life review of the facility ductwork by an independent corrosion engineer. The review identifies emerging corrosion before it becomes a closure event.
• Maintain the as-built drawings in a controlled facility document register. The drawings will be needed for every renovation, every accreditation visit and every emergency response over the 30 year facility life.
• Train the maintenance team on the consequences of unplanned duct work. Cutting into a PC3 supply duct for an unplanned diffuser relocation breaks the envelope; the recovery requires a full decontamination cycle and re-validation. The training avoids the unplanned cut.

How SBKJ supports animal-facility ductwork projects

SBKJ Group supports Australian and international animal-facility ductwork projects with three things: machinery, engineering support and after-sales continuity.

Machinery — the SBAL-V stainless auto duct line, the SBTF-1602 spiral tubeformer and the TIG longitudinal seam welder are the core supply for stainless animal-facility ductwork fabrication. Every machine is CE-marked under Machinery Directive 2006/42/EC, ISO 9001:2015 quality-system manufactured, supplied with full FAT documentation and commissioned on the buyer's site by SBKJ engineers. The machines are configured at quotation stage to the buyer's coil specification — width, gauge, alloy and supply voltage — never on a generic brochure assumption.

Engineering support — SBKJ engineers respond to pre-purchase technical questions within 12 hours, supply CAD layout drawings, single-shift output figures measured against the buyer's coil and PLC source-code escrow agreements. After commissioning, the same engineers support 72-hour response on remote service via WhatsApp, email or video call.

After-sales continuity — SBKJ supplies original spare parts for any commissioned machine for at least ten years, in writing. Our oldest in-service machines were commissioned in the early 2000s; we are still shipping spare parts to those installations today. The spare parts-continuity guarantee is not a marketing claim; it is a contractual commitment we honour because our installed base in the animal-facility ductwork sector — across Australian university vivariums, teaching hospitals, contract research organisation animal blocks, and pharmaceutical research animal facilities — depends on it.

Closing — the long view

Animal-facility ductwork is the boring infrastructure that holds the entire welfare and biosafety case for an institution together. It runs every minute of every day for thirty years. It survives ammonia, decontamination cycles, steam, formaldehyde and the cumulative wear of every door opening every day. It is the engineering substrate underneath the Animal Ethics Committee approval, the AAALAC accreditation certificate and the research output of every animal study the institution publishes.

Specifying it correctly at concept design — 304 minimum, 316L where decontamination chemistry demands, spiral round preferred, fully-welded inside the PC3 envelope, HEPA H14 in bag-in-bag-out housings on every contamination-class exhaust, 100 percent outside air for animal holding, pressure cascade resilient to door opening, materials matched to the planned and foreseeable decontamination chemistry — is the cheapest insurance the institution will buy in the entire facility lifecycle. Skipping it costs a closure event in year three, an unplanned 316L retrofit in year five, an AAALAC site visit conditional accreditation in year seven and a complete envelope rebuild in year ten.

SBKJ Group supplies the machinery, the engineering and the after-sales continuity that Australian animal-facility ductwork fabricators rely on to fabricate ductwork that lasts the design life of the building. If you are designing, fabricating or operating an Australian animal facility — Greencross or Vetwest or Animal Referral Hospital expansion build, Lort Smith or Royal Melbourne Veterinary Specialist Centre clinical refit, Murdoch or University of Queensland or University of Adelaide veterinary teaching precinct, WEHI or Garvan or Peter MacCallum or QIMR Berghofer or Mater or Monash BDI or Telethon Kids vivarium build, CSL Behring vivarium operations — the SBKJ engineering team is available to answer specification questions within 12 hours.

Ask an SBKJ engineer about your animal-facility ductwork →

FAQ

What air change rates apply to animal holding rooms in research vivariums?

10 to 15 ACH for general animal holding, 15 to 20 ACH for procedure and surgical, 20 to 25 ACH for primate, dog and high-density rodent rooms. 15 ACH minimum for cage wash and necropsy with 100 percent outside air. No recirculation between holding rooms.

What pressure cascade is required between clean and dirty zones?

Clean change rooms at +15 to +25 Pa, corridor at 0 Pa, holding rooms at -15 to -25 Pa, necropsy at -30 Pa, with anterooms at intermediate pressures for PC3 and PC4. PC4 facilities have a sealed envelope with HEPA on both supply and return.

Why does galvanised ductwork fail in animal facilities?

Ammonia from urine etches the zinc within 12-24 months; decontamination chemistry strips zinc within months; cage wash steam at 38 degrees Celsius and 100 percent humidity causes white rust and pitting. 304 stainless is the minimum specification; 316L is mandatory for cage wash, necropsy and decontamination plenums.

What HEPA filter grade is required for PC2, PC3 and PC4 facilities?

HEPA H14 (greater than 99.995 percent at MPPS). PC2 filters biological safety cabinet exhaust only. PC3 filters room exhaust through bag-in-bag-out housings. PC4 filters both supply and return with redundant banks.

Why are spiral round ducts preferred over rectangular?

Fewer corners reduce harbourage for biological contamination, the continuous spiral seam is straightforward to weld, pressure loss is roughly 20 percent lower than equivalent rectangular ductwork, and decontamination penetrates whole-bore more uniformly.

How is formaldehyde managed in necropsy rooms?

Downdraft tables with dedicated exhaust through 316L stainless ductwork to atmosphere via HEPA and activated carbon. No recirculation. Time Weighted Average kept below 0.75 ppm Occupational Exposure Limit; Short Term Exposure Limit below 2 ppm.

What SBKJ machines are appropriate for stainless veterinary and vivarium ductwork?

The SBAL-V stainless auto duct line for rectangular ducts, the SBTF-1602 spiral tubeformer for round ducts up to 1,600 mm diameter, and a TIG longitudinal seam welder for fully-welded biocontainment seams. All CE-marked under Machinery Directive 2006/42/EC.