Hospital Operating Theatre, ICU, Cath Lab, MRI/CT Radiology and Specialty Surgical Wing HVAC Duct Guide — ASHRAE 170, AS 1668.2, AHFG

Why the operating theatre is the most demanding HVAC environment in any hospital

An operating theatre is the most tightly controlled clinical environment in the entire hospital. The patient on the table is, for the duration of the procedure, immunologically defenceless — the surgical incision opens a direct conduit from theatre air to deep tissue and bone, the anaesthetised patient cannot shiver to regulate body temperature, and the surgical team standing over the field carries skin squamae and respiratory aerosol that must be moved away from the wound rather than into it. The HVAC system is what makes the operating theatre work. It is not a comfort system. It is a clinical engineering control on surgical site infection, on staff exposure to anaesthetic gas, on the heat load from surgical lights, video integration pendants, intra-operative imaging and a team of six to twelve clinicians in surgical drapes, and on the temperature window that protects an open-chest cardiac patient or an orthopaedic joint-replacement recipient from intra-operative hypothermia.

The numbers a hospital HVAC engineer works to are not arbitrary. ASHRAE Standard 170-2021, the international ventilation reference framework for healthcare facilities, calls for 20 air changes per hour minimum and 4 ACH minimum outdoor air in a Class B / C operating theatre, at a positive pressure relative to surrounding spaces, with terminal HEPA filtration over the surgical field. The Australasian Health Facility Guidelines — the room-by-room functional briefing document maintained by the AHIA Australasian Health Infrastructure Alliance and adopted by every state health infrastructure authority — aligns with ASHRAE 170 and adds Australian-specific room areas, finishes, equipment loads and clinical workflow patterns. The legal floor in Australia is AS 1668.2 (mechanical ventilation in buildings), which is the National Construction Code reference and is non-negotiable. Sitting above all three is the National Safety and Quality Health Service Standards (NSQHS) 2nd edition framework administered by the ACSQHC Australian Commission on Safety and Quality in Healthcare — the accreditation regime that every hospital in Australia is audited against.

That stack of standards, guidelines and accreditation frameworks is layered on top of a stack of room types. A modern teaching hospital perioperative precinct contains general theatres, orthopaedic theatres, cardiac theatres, neurosurgical theatres and hybrid ORs with integrated angiography or CT or MRI — each with different temperature, humidity, ACH, filtration and pressure requirements. Sitting immediately adjacent are the anaesthetic induction rooms, scrub bays, sterile core, dirty utility and PACU recovery. Downstream are the ICU and HDU. Across the corridor are the cath labs and electrophysiology suites. One floor down are the MRI and CT scanners with their own quench-pipe and shielded-room complications. Beyond all of those are the airborne infection isolation rooms, the protective environment isolation rooms for bone marrow transplant patients, the cytotoxic compounding pharmacy that supplies the oncology infusion units, the nuclear medicine hot lab, the bronchoscopy suite, the hyperbaric oxygen chamber, the burns unit, the NICU and the trauma resuscitation bay.

This guide is the design reference SBKJ engineers in Box Hill North Victoria use when briefed by mechanical consultants and fit-out contractors fabricating ductwork for Australian public and private hospital perioperative and critical-care projects. It walks through the regulatory framework, zone-by-zone specification, material selection, fabrication and commissioning sequence, verification protocol and operational handover. It is not a substitute for a registered mechanical engineering design, an AHFG compliance review by an accredited healthcare design consultant, or a project-specific NSQHS accreditation cycle.

The Australian regulatory and standards stack

Hospital perioperative and critical-care HVAC ductwork in Australia is governed by a layered stack of mandatory standards, advisory guidelines, professional codes and organisational accreditation frameworks. No single document gives the complete picture, and designers who anchor to one and ignore the others end up with non-compliant or over-specified work. The stack we work with on every operating theatre, ICU, cath lab and specialty surgical project, in priority order, is set out below.

Mandatory Australian Standards (legal floor under the NCC)

• AS 1668.2 — mechanical ventilation in buildings. This is the legal floor under the National Construction Code. It defines minimum outdoor air, minimum exhaust rates, ventilation effectiveness and contaminant control. AS 1668.2 alone is not sufficient for hospital perioperative HVAC — ASHRAE 170 and AHFG always sit above it — but a design that fails AS 1668.2 will not pass building certification.
• AS 4254 — ductwork construction (parts 1 and 2 for flexible and rigid duct). Defines duct class, leakage class, sealing class, reinforcement, support spacing and the joint patterns acceptable in Australian practice. Perioperative ductwork is typically AS 4254 Class B or Class C, SMACNA Seal Class A.
• AS/NZS 1530.4 — fire-resistance test for elements of construction. Drives the fire-rated duct, fire damper and shaft penetration design. Every hospital ductwork crossing of a fire-rated wall, floor or shaft is detailed against AS/NZS 1530.4 fire-resistance levels (FRLs) per the NCC Section C requirements.
• AS 3000 — wiring rules. Governs the electrical installation of HVAC plant, BMS, dampers, fan motor circuits and the medical electrical equipment isolation regime per AS/NZS 3003.
• AS 4032 — medical gas pipeline systems (parts for oxygen, medical air, nitrous oxide, surgical compressed air, medical vacuum and AGSS anaesthetic gas scavenging). Defines the medical gas distribution that the HVAC must coordinate with at the OR ceiling pendant, the wall outlets in PACU and ICU, and the AGSS exhaust duct that the HVAC integrates.
• AS 4044 — medical gas alarm systems. Defines the alarm regime for medical gas pressure, flow and contamination. The HVAC BMS integrates the AGSS exhaust performance into the medical gas alarm framework.
• AS 2896 — medical gas systems — the umbrella standard covering valve panels and isolation panels at every clinical zone. Coordinates with AS 4032 and AS 4044.
• AS 1851 — fire damper, smoke damper, fire/smoke combination damper and fire-rated duct testing and maintenance. Drives the duct system inspection and test regime for the life of the building.
• AS 2118 — automatic sprinkler systems. Coordinates with the HVAC duct routing through fire-rated zones and the smoke management strategy.
• AS 4214 — gaseous fire suppression systems. Relevant in the MRI suite (where water sprinkler activation in the magnet room would short the cryostat and the gradient electronics), in the cath lab control room and in some imaging equipment rooms where gaseous suppression replaces sprinklers.
• AS/NZS 60079-10-1 — classification of explosive gas atmospheres. Relevant only in the immediate envelope of the hyperbaric oxygen chamber and in any oxygen-enriched zone where Zone 2 classification applies. Spark-resistant aluminium duct construction is mandated in the Zone 2 envelope. The standard is rarely invoked elsewhere in the perioperative precinct.
• AS 1940 — storage and handling of flammable and combustible liquids. Relevant to the storage of anaesthetic ether (largely historical), some sterilants and the alcohol-based hand-rub bulk store.
• AS 1716 — respiratory protective devices. Relevant to the staff respiratory protection regime in AIIR and in the cytotoxic compounding pharmacy. The HVAC engineering controls reduce reliance on respiratory protection but never eliminate it.
• AS 1530.3 — simultaneous ignitability tests. Relevant to anaesthetic mask and oxygen cylinder selection in the perioperative envelope.
• AS/NZS 2243.3 — microbiological safety and containment. Relevant to the cytotoxic compounding pharmacy biological safety cabinet exhaust and to the pathology/laboratory zones adjacent to the operating theatre suite. Where laboratory work crosses into the OR precinct, AS/NZS 2243.3 governs.
• AS/NZS 4187 — reprocessing of reusable medical devices. Drives the Theatre Sterile Services Unit (TSSU) co-located with the OR suite and the wider CSSD relationship. Refer the CSSD HVAC duct guide for the full sterile services pressure cascade.
• AS 4815 — office-based health care facilities. Drives the day-surgery and specialist consulting room ductwork that sits outside the major hospital envelope. Refer the dental clinic and surgery HVAC duct guide for the AS 4815 design pattern.
• AS 5369 — reprocessing of reusable medical devices in health service organisations. Companion to AS/NZS 4187 covering the broader reprocessing context.

International standards used as the technical reference

• ASHRAE Standard 170-2021 — ventilation of healthcare facilities. The international reference framework. AHFG aligns with it; SBKJ engineering practice follows it as the default position. Defines ACH, outdoor air, filtration grade, pressure relationship and supply/return airflow pattern for every room type in a healthcare facility.
• ASHRAE Standard 62.1 — ventilation for acceptable indoor air quality. Underpins the outdoor air component of ASHRAE 170.
• ISO 14644 series — cleanroom classification. ISO Class 5 (the at-rest target directly under an OR laminar field), ISO Class 7 (cytotoxic compounding pharmacy buffer area) and ISO Class 8 (general OR background and CSSD packing). ISO 14644-3 covers test methods; ISO 14644-7 covers separative enclosures including the laminar flow OR ceiling.
• ISO 29463 — HEPA filter classification (H13, H14) replacing the legacy EN 1822 designation in most current procurement language. The terminal filter on every OR, PE room, cath lab and cytotoxic anteroom is classified to ISO 29463.
• IEST-RP-CC034 — HEPA filter leak testing. The PAO challenge and photometer scan protocol used at commissioning and annual re-verification.
• SMACNA HVAC Duct Construction Standards — the international ductwork construction reference, particularly the Seal Classes (A, B, C) which the Australian perioperative HVAC industry uses as a shorthand even where AS 4254 is the formal standard.
• NFPA 99 — healthcare facilities code. Used as a reference framework for medical gas, electrical and HVAC integration; not mandatory in Australia but referenced by some healthcare consultants alongside AS 4032 and AS 1668.2.

Australian advisory guidelines and accreditation

• AHFG — Australasian Health Facility Guidelines (latest version, maintained by the AHIA). The room-by-room functional briefing document for every healthcare facility in Australia and New Zealand. Adopted by every state health infrastructure authority for public hospital projects and used as the design reference by private hospital operators. The HVAC section of each Health Planning Unit (HPU) defines pressure, ACH, temperature, humidity and filtration. AHFG references ASHRAE 170 explicitly. For perioperative work, refer HPU 510 Operating Suite, HPU 350 Intensive Care, HPU 510.2 Cath Lab, HPU 320 Medical Imaging, HPU 590 Day Procedure Unit.
• NSQHS Standards 2nd edition — National Safety and Quality Health Service Standards. The accreditation regime administered by ACSQHC. The HVAC design must support the organisation's NSQHS compliance, particularly Standard 3 (preventing and controlling healthcare-associated infections).
• ACSQHC — Australian Commission on Safety and Quality in Healthcare. The accreditation authority. ACSQHC publishes the Australian Guidelines for the Prevention and Control of Infection in Healthcare jointly with NHMRC; the document drives the AIIR, PE and bronchoscopy ventilation expectations.
• NHMRC Australian Guidelines for the Prevention and Control of Infection in Healthcare (joint with ACSQHC). The infection control reference framework. Defines transmission-based precautions and the engineering controls that support them.
• ICEAA — Infection Control and Epidemiology Australia. The professional body of infection prevention specialists. Their position statements inform AIIR design beyond the bare ASHRAE 170 / AHFG minima.
• IHEA — Institute of Healthcare Engineering Australia. The professional body of hospital engineers. IHEA's NSW, VIC and QLD chapters host the conferences and CPD that drive the working knowledge of HVAC operations in Australian hospitals. The IHEA Technical Guidelines on healthcare ventilation are referenced in many engineering briefs.
• State health engineering standards — NSW Health Engineering Services Guidelines, VIC DH Engineering Standards, QLD Health Technical Service guides, SA Health Infrastructure standards, WA Department of Health Engineering Services standards, ACT Health Infrastructure standards, Tasmanian Department of Health technical guides, NT Department of Health engineering reference. Each adds state-specific requirements that supplement the AHFG.
• TGA — Therapeutic Goods Administration. Governs the medical devices used in the OR and the sterile barrier inventory; the HVAC supports the TGA compliance posture rather than being directly regulated by TGA.

Workplace exposure standards (Safe Work Australia)

The HVAC system is the principal engineering control that keeps clinical staff inside the Safe Work Australia workplace exposure standards (WES) for the chemical agents present in the perioperative envelope. The relevant agents and their published WES limits are set out below; SBKJ engineering practice is to size exhaust and supply to achieve a comfortable margin below the WES on a continuous basis (typically 25 to 50 percent of WES at breathing height), not to operate at the WES as a target.

• Nitrous oxide (N₂O), used as an anaesthetic carrier and adjunct: 25 ppm 8-hour TWA.
• Isoflurane, sevoflurane and desflurane (volatile halogenated anaesthetics): 50 ppm 8-hour TWA each. Sevoflurane is the most commonly used in current Australian practice.
• Formaldehyde, used in some pathology and morgue applications and in some chemical disinfection chemistries: 1 ppm STEL.
• Glutaraldehyde, used in some manual high-level disinfection of endoscopes: 0.05 ppm STEL.
• Ortho-phthalaldehyde (OPA), used in current automated endoscope reprocessing: no published WES, treated as a sensitiser with engineering controls to keep airborne exposure as low as reasonably practicable.
• Peracetic acid, used in automated endoscope reprocessing and in some low-temperature sterilisation chemistries: 0.4 ppm STEL.
• Ethylene oxide (EtO), used historically in some low-temperature sterilisation (now largely replaced by hydrogen peroxide): 1 ppm STEL.
• Ozone, used in some sanitisation cycles: 0.1 ppm 8-hour TWA.
• Methyl methacrylate (MMA), used in orthopaedic bone cement: 50 ppm 8-hour TWA.
• Styrene, used in some orthopaedic and prosthetic applications: 50 ppm 8-hour TWA.
• Ammonia, used as a refrigerant in some hospital cold rooms and as a Sterrad cycle by-product: 25 ppm 8-hour TWA.
• Oxygen: ambient 19.5 to 23.5 percent for safe working. WES upper limit 23.5 percent for enriched atmospheres — relevant to PACU, ICU, hyperbaric chamber room, NICU and any clinical space with continuous medical oxygen delivery.
• Helium (He): inert, no formal WES, but the asphyxiation hazard from MRI cryogen quench discharge is governing on quench-pipe design and discharge location.
• Nitrogen (N₂): inert, no formal WES, but the asphyxiation hazard from medical liquid nitrogen storage and from cryogenic specimen storage applies.

The operating theatre HVAC envelope — designing for ISO Class 5 at the surgical site

The operating theatre is the most demanding HVAC zone in the hospital, and the laminar flow ceiling plenum directly over the surgical table is the most demanding fabricated item in the entire perioperative HVAC package. Get the plenum right and the rest of the theatre HVAC is conventional. Get the plenum wrong and no amount of downstream filtration, BMS sophistication or commissioning effort will recover an OR that fails its ISO 14644 particle count.

Theatre classification and the ISO 14644 target

ASHRAE 170-2021 classifies hospital ventilation zones as Class A, Class B or Class C. Class A applies to invasive procedures performed under local anaesthetic in a procedural room. Class B applies to invasive procedures under regional or general anaesthetic. Class C applies to invasive procedures involving the body cavity, the central nervous system or implant insertion. In Australian practice, every general operating theatre is treated as Class B/C, and the orthopaedic, cardiac and neurosurgical theatres at the upper boundary of Class C. The AHFG follows the ASHRAE classification and adds Australian-specific room area and finishes requirements.

The ISO 14644 cleanliness target is more granular. The general OR is designed to ISO Class 7 at-rest in the room background, with the area directly under the laminar flow ceiling plenum achieving ISO Class 5 at-rest while the laminar field is operating. ISO Class 5 means no more than 3,520 particles greater than or equal to 0.5 micron per cubic metre — a cleanliness comparable to a pharmaceutical fill-line Grade A under EU GMP Annex 1. The orthopaedic, cardiac and neurosurgical theatres push the target further, with ISO Class 5 maintained out to the wall edge of the laminar field (a 3.0 by 3.0 metre footprint) and ISO Class 6 at the perimeter of the theatre. Validation is by ISO 14644-1 particle counting at commissioning and annually thereafter, with the commissioning record retained in the NSQHS quality file.

Air change rate, outdoor air and the heat-load balance

ASHRAE 170 requires 20 ACH minimum supply and 4 ACH minimum outdoor air in a Class B / C operating theatre. SBKJ engineering practice is to size the supply at 25 ACH for general OR and 25 to 30 ACH for orthopaedic, cardiac and neurosurgical theatres. The uplift over the ASHRAE minimum recognises that modern surgical light arrays (LED clusters dissipating 200 to 400 watts each), video integration ceiling pendants (300 to 600 watts), intra-operative imaging C-arms (8 to 15 kilowatts continuous) and the heat output of the surgical team in drapes (200 to 300 watts per person, six to twelve people) together drive a heat load that ASHRAE 170's bare minimum struggles to remove while holding the temperature window. A typical orthopaedic theatre runs at 12 to 18 kilowatts sensible heat load excluding any intra-operative imaging.

The temperature window itself is a clinical control. ASHRAE 170 specifies 20 to 24 degrees Celsius for general OR. SBKJ engineering practice is to design for 17 to 21 degrees Celsius for orthopaedic and cardiac (which run cooler to manage the heat stress on the surgical team in lead aprons and double-layered orthopaedic drapes, and to support intra-operative hypothermia protocols on cardiac bypass) and 20 to 23 degrees Celsius for general OR. The relative humidity envelope is 30 to 60 percent in all theatres; below 30 percent RH static electricity becomes a concern (historically with flammable anaesthetics, currently with electronic equipment), above 60 percent RH condensation on cold surfaces and microbial growth on packaging become concerns. The supply air is therefore a balance: enough volume to maintain ACH and remove heat, conditioned to the temperature and humidity envelope, with 4 ACH minimum outdoor air to dilute anaesthetic gas and CO₂.

The laminar flow ceiling plenum — the heart of the OR HVAC

The terminal supply over the surgical table is a laminar flow ceiling plenum: a rectangular pressurised housing that distributes filtered air evenly across a 2.4 by 2.4 metre face (general OR), 3.0 by 3.0 metre face (orthopaedic, cardiac, neuro) or 3.6 by 3.6 metre face (hybrid OR with extended sterile field). The face carries HEPA filter modules (typically 610 by 610 millimetre or 610 by 1,220 millimetre per the manufacturer's filter standard) in non-aspirating diffusers with gel seal frames and knife-edge gaskets. Face velocity through the filter face is 0.20 to 0.30 metres per second downward — the "laminar field" that gives the plenum its name.

The plenum is fabricated from Type 304 stainless steel or G90 galvanised steel on AS 4254 Class B (medium-pressure, 750 Pa) construction, continuously sealed to SMACNA Seal Class A. Every joint is gasketed and mastic-sealed; every seam on the stainless content is TIG-welded longitudinally; every penetration through the plenum shell (drop rods, electrical conduit, sensor connections) is gasketed and sealed. The plenum is the engineering quality test for the duct fabricator. A 2-millimetre out-of-square on a filter seat compromises the gel seal and the filter leaks past the frame. A poorly aligned plenum drop wastes the entire downstream filtration investment. The fix is precision fabrication on the plenum boxes — typically on the SBAL-V auto duct line with dimensional control on the cutting and folding operations, finished with stitchwelded longitudinal seams on the SB-ZF1500 automatic stitchwelder — rather than site-fabrication that depends on hand-shimming for fit.

Upstream of the plenum the supply duct sits inside the ceiling void, routed clear of the OR's medical gas pendants, surgical light suspension and video integration trays. Plenum access for filter change-out is from the top (the technical ceiling) rather than from inside the OR — HEPA change is a maintenance operation that should not require taking the OR out of clinical use. The access hatches are gasketed, sealed and pressure-tested as part of the commissioning sequence.

HEPA grade selection and the IEST-RP-CC034 protocol

ASHRAE 170 and AHFG require HEPA H13 minimum at the terminal supply for Class B and Class C theatres. SBKJ engineering practice is to specify HEPA H14 (per ISO 29463) at the laminar flow ceiling plenum for orthopaedic, cardiac, neuro and implant surgery, achieving an at-rest particle count comfortably inside ISO Class 5 directly under the laminar field. H13 captures 99.95 percent of 0.3 micron particles at MPPS; H14 captures 99.995 percent — a tenfold reduction in penetration that translates to a measurable reduction in particle counts at the wound when the surgical team is moving.

Every terminal HEPA is tested at commissioning per IEST-RP-CC034: a PAO challenge upstream of the filter face and a photometer scan across the downstream face. Acceptance is no penetration above 0.01 percent at any point on the filter face or frame seal. Annual re-testing follows the same protocol. The plenum design must support the test: upstream PAO injection port, downstream photometer scan port with a metre-by-metre grid pattern accessible from the technical ceiling. SBKJ pre-fabricates the test ports into the plenum at the workshop — site retrofitting of test ports is a frequent commissioning failure point.

Return air strategy — the four-corner low wall pattern

Operating theatre return is via low wall grilles at each of the four corners of the theatre, at floor level (300 to 600 millimetres above finished floor), sized for a face velocity of 1.5 to 2.5 metres per second. The four-corner low return strategy combined with the terminal laminar ceiling drives a top-down clean-to-dirty airflow: clean filtered air enters at the ceiling, passes over the surgical field, and exits at the floor carrying particulate and skin squamae away from the wound. Avoid high return grilles in the OR — they short-circuit the laminar field by drawing the descending column of clean air back up through the perimeter of the room before it can sweep the floor.

The return ductwork is fabricated to AS 4254 Class B on galvanised steel where the return air is theatre-only (no cross-contamination risk) or Type 304 stainless where the return path serves an isolation room and the duct passes leak-tight integrity testing. The return path can be recirculated through the theatre AHU per ASHRAE 170 with the recirculated fraction passing through the AHU's pre-filter and final filter banks; alternatively, where the design opts for 100 percent outdoor air (the safest specification but the most expensive to operate) the return is fully exhausted. The 100 percent outdoor air option is the SBKJ recommendation for orthopaedic, cardiac and neuro theatres; partial recirculation is acceptable for general OR provided the recirculation HEPA train meets the manufacturer's certification at full design flow.

The hybrid operating theatre — integrated imaging and the extra HVAC burden

A hybrid operating theatre — an OR with integrated intra-operative angiography (typically a fixed C-arm or biplane angiography), CT or MRI — is the design pattern for cardiac, vascular, neurosurgical and complex oncological surgery where the surgical team needs to acquire imaging during the case without moving the patient out of the sterile field. The hybrid OR is now standard equipment in every tertiary teaching hospital in Australia — Royal Melbourne, Royal Prince Alfred, Royal Brisbane and Women's, Royal Adelaide, Sir Charles Gairdner, Fiona Stanley, Canberra and the Alfred all run multiple hybrid theatres — and is increasingly common in private cardiac centres operated by Ramsay Health Care, Healthscope and St Vincent's.

The hybrid OR carries the same surgical-grade HVAC fundamentals as a standalone OR: 25 ACH minimum supply through a laminar HEPA H14 ceiling plenum (typically 3.0 by 3.0 metres minimum, often 3.6 by 3.6 metres to accommodate the extended sterile field for vascular and neurosurgical hybrid procedures), +10 to +15 Pa positive to corridor and to the adjacent control room, 30 to 60 percent humidity, 17 to 21 degrees Celsius for cardiac and orthopaedic hybrid indications. The plenum may need a cut-out or asymmetric layout to clear the C-arm's overhead suspension; the cut-out is detailed at design stage with the imaging equipment installer because retrofitting the plenum after install is expensive and disruptive.

What the hybrid OR adds is dedicated cooling capacity for the imaging equipment. A fixed C-arm angiography unit rejects 8 to 15 kilowatts continuous through its dedicated cooling supply — supplied either by an independent chilled water connection direct to the equipment rack or by HVAC supply air dedicated to the equipment-rack cabinet. Intra-operative CT (the "CT-on-rails" configuration used at the Alfred Hospital trauma hybrid and at Royal Melbourne) and intra-operative MRI (used at the Royal Children's Hospital and at the Walter and Eliza Hall Institute hybrid suite) reject more — 25 to 40 kilowatts for intra-operative CT, 40 to 70 kilowatts continuous for intra-operative MRI. The supplemental cooling supply is routed at the perimeter clear of the laminar field; in the intra-operative MRI configuration the supplemental cooling is RF-cabinet-aware and uses the same wave-guide treatment at the cabin penetrations as the principal supply.

For the intra-operative MRI hybrid OR, the full MRI suite cryogen quench discharge applies (refer the MRI section below). The quench pipe is routed clear of the laminar plenum — the routing is detailed with the imaging equipment installer because a quench event with a misrouted pipe drops 1,500 to 2,000 litres of liquid helium volume worth of cold gas into the building envelope. The shielded RF cabin around the magnet uses copper or aluminium panel construction with all HVAC duct penetrations treated by wave-guide or honeycomb panel matched to the cabin manufacturer.

Coordination at design stage is governing. Every hybrid OR project SBKJ has supplied ductwork into has run a multi-discipline design coordination workshop with the surgeon-lead, the radiologist-lead, the anaesthetist-lead, the perfusionist (for cardiac hybrid), the mechanical engineer, the medical physicist and the imaging equipment installer's project engineer in the same room for a half-day session. The coordination output drives the plenum cut-out detail, the supplemental cooling layout, the quench-pipe routing where applicable, the medical gas pendant location and the video integration tray layout. Skipping the coordination workshop is the single most expensive design choice on a hybrid OR; the cost of post-install rework on a hybrid theatre that is already commissioned for surgical use is measured in millions of dollars per theatre.

The cath lab and electrophysiology suite

Cardiac catheterisation laboratories and electrophysiology (EP) suites perform invasive cardiac procedures — coronary angiography, percutaneous coronary intervention, ablation, pacemaker and defibrillator implantation, transcatheter aortic valve implantation (TAVI), structural heart procedures — under sterile conditions but generally without the deep-cavity surgical exposure of an open-chest cardiac theatre. The HVAC classification under ASHRAE 170 is Class B / C with the design target one step less demanding than a full cardiac OR but materially more demanding than a general procedural room.

Cath lab HVAC specification

Pressure: +5 to +10 Pa positive to corridor, neutral to the control room. Supply: 20 ACH through a HEPA H13 ceiling plenum (face dimensions typically 1.8 by 1.8 metres over the procedure table) with 4 ACH minimum outdoor air. Humidity: 30 to 60 percent. Temperature: 20 to 23 degrees Celsius. Return: low wall grilles at the corners of the room, sized for 1.5 to 2.5 metres per second face velocity. The cath lab does not require a full laminar field over the procedure table the way an orthopaedic theatre does — the surgical exposure is via a femoral or radial access point under sterile drape rather than an open body cavity — but the supply plenum is still HEPA H13 terminal in non-aspirating diffusers.

Fluoroscopy shielding integration

The cath lab carries fixed C-arm fluoroscopy generating significant ionising radiation. The wall and ceiling assemblies are lead-shielded to a thickness specified by the radiation physicist (typically 2 to 4 millimetres lead equivalent for the cath lab walls, with higher shielding behind the C-arm). HVAC duct penetrations through shielded boundaries are detailed with lead-jacketed sleeves and lead-equivalent damper sleeves so that ionising radiation cannot pass through a duct penetration. The radiation physicist sign-off is part of the commissioning binder; the HVAC engineer cannot release the cath lab without the radiation physicist's shielding integrity test.

Equipment cooling supplemental

The cath lab fluoroscopy generator, the haemodynamic monitoring system and the electrophysiology mapping system together reject 6 to 12 kilowatts continuous heat. The equipment rack is typically in a separately-conditioned equipment room adjacent to the cath lab proper; the cath lab itself carries the patient and clinician heat load plus the C-arm tube heat. SBKJ engineering practice is to size the cath lab supply at the upper end of the 20 ACH band to absorb the equipment heat load through air handling rather than running a separate chilled water tap to the cath lab proper.

Electrophysiology suite specifics

The EP suite differs from the cath lab in two respects. First, EP procedures (atrial fibrillation ablation, ventricular tachycardia ablation, accessory pathway ablation, complex re-entrant tachycardia ablation) typically run 4 to 8 hours per case where a cath lab case runs 30 to 90 minutes. The HVAC must sustain the airflow and temperature envelope continuously for a working day per room. Second, the EP suite carries additional electrophysiology mapping equipment — the CARTO or EnSite mapping system, the 64-channel electrophysiology recorder, the radiofrequency or cryoablation generator — each of which adds heat and electrical load. The HVAC specification is otherwise the same as the cath lab: +5 to +10 Pa, 20 ACH, HEPA H13 terminal, lead shielding integrated. SBKJ supply ductwork is typically Type 304 stainless on the supply plenum and galvanised on the return, the same pattern as the cath lab.

The interventional radiology room

Interventional radiology (IR) performs image-guided minimally invasive procedures — transjugular intrahepatic portosystemic shunt (TIPS), embolisation of vascular malformations and tumours, biopsy, drainage of abscess and collection, vascular access procedures, neuro-IR (mechanical thrombectomy for ischaemic stroke, coiling and stent-assisted coiling of intracranial aneurysms). The HVAC profile sits between the cath lab and a general procedure room. Pressure: +5 to +10 Pa positive to corridor. Supply: 15 to 20 ACH through HEPA H13 ceiling plenum (1.8 by 1.8 metres over the procedure table). Humidity: 30 to 60 percent. Temperature: 20 to 23 degrees Celsius.

The procedure mix drives the upper end of the ACH band. TIPS and complex neuro-IR procedures run 2 to 6 hours per case and carry the same surgical-grade infection control concern as a cath lab; embolisation and biopsy are shorter and lighter. The lead shielding and the radiation physicist sign-off mirror the cath lab. The IR suite typically sits adjacent to the cath lab and the EP suite in a unified cardiac and vascular procedural precinct, sharing the control room, the recovery bay and the medical gas distribution. The HVAC design treats the suite as a precinct rather than as individual rooms — the supply AHU, the return AHU, the BMS pressure cascade and the medical gas integration are designed across the precinct, with each room getting its dedicated terminal supply and return.

The intensive care unit and high-dependency unit

The ICU and HDU are the highest-acuity inpatient zones in the hospital. The HVAC profile is calibrated to support critically unwell patients, intubated and ventilated patients, post-surgical patients in the early recovery phase, patients on extracorporeal membrane oxygenation (ECMO), patients on continuous renal replacement therapy (CRRT) and patients in the late phase of a complex critical illness who may be shedding multi-drug-resistant organisms or airborne pathogens.

ICU bedspace HVAC specification

Pressure: +5 Pa positive to corridor. Supply: 6 ACH with 2 ACH minimum outdoor air per ASHRAE 170. Humidity: 40 to 60 percent. Temperature: 22 to 24 degrees Celsius. Individual bedspace with full-height privacy partition or full wall and door per the AHFG (the modern ICU design pattern is single-room cubicles with full wall and door for infection control, replacing the legacy multi-bay open-plan ICU). Each bedspace gets a dedicated supply diffuser at the head of the bed and a dedicated return path to the suite return duct.

ICU airflow direction and clinician protection

ICU patient airflow strategy is calibrated to clinician exposure. Clean filtered supply air enters at the head of the bed — behind and slightly above the patient's head. Return is at the foot of the bed or low wall at the foot. Respiratory secretions and aerosol travel from the patient airway downward and toward the foot of the bed, away from the clinician working at the head (intubation, suctioning, oral care, line management). The supply-to-return geometry is critical: getting it backwards (return at the head, supply at the foot) sweeps every patient aerosol directly across the clinician's breathing zone. SBKJ has detailed dozens of ICU duct layouts on Australian projects and the head-of-bed supply / foot-of-bed return is the universal pattern.

ICU isolation conversion capability

A proportion of ICU beds in every modern Australian ICU (typically 1 in 6 to 1 in 10, with 1 in 4 in tertiary teaching ICUs after the COVID-19 experience) is built with the capability to convert to a negative-pressure airborne infection isolation configuration. The conversion is by activation of a dedicated single-pass exhaust fan and reversal of the room's pressure relationship to corridor. The ductwork must support the conversion: the dedicated exhaust path is built into the room at construction, terminating at a HEPA H13 housing on the roof, and the conversion is by BMS command and damper reposition rather than physical duct re-routing. The capability requires careful design at construction; retrofitting an existing ICU bed to negative-pressure capability is a major works exercise.

HDU step-down specification

The HDU step-down (sometimes called sub-intensive care or progressive care) uses the same pattern at lower ACH (4 to 6 ACH supply, 2 ACH outdoor air, +5 Pa positive to corridor). HDU patients are stable enough to step out of the ICU but still require continuous monitoring and may still be on non-invasive ventilation or supplemental oxygen. The HVAC envelope is essentially a clinical ward bedspace with ICU-grade infection control posture.

Airborne infection isolation rooms

An airborne infection isolation room (AIIR) is engineered to contain a patient who is shedding an airborne-transmissible pathogen — Mycobacterium tuberculosis, measles virus, varicella-zoster virus, SARS-CoV-2, novel respiratory viruses with airborne transmission — so that the air the patient exhales does not enter the rest of the hospital. The AIIR is the principal infection control engineering response in every Australian tertiary hospital and is the room type that came under the most scrutiny during the COVID-19 pandemic.

AIIR specification

Pressure: -5 to -10 Pa negative to anteroom and corridor (ASHRAE 170 minimum is -2.5 Pa; SBKJ engineering practice is the deeper cascade for robust performance during door operation). Supply: dedicated supply air from the AHU through MERV 13 minimum filtration, delivered at the head of the bed via non-aspirating diffuser. Exhaust: 12 ACH minimum single-pass exhaust through HEPA H13 at the room exhaust grille or at the rooftop discharge before atmospheric release, no recirculation back to the building. Humidity: 40 to 60 percent. Temperature: 22 to 24 degrees Celsius. Anteroom buffer: anteroom at +5 Pa to AIIR and neutral to corridor — air flows corridor → anteroom → AIIR → HEPA exhaust to outdoor. Door-side pressure indicators at the anteroom entry and the AIIR entry; BMS alarming on cascade loss.

The single-pass exhaust path

The AIIR exhaust duct is the single most safety-critical ductwork element in the hospital after the operating theatre laminar plenum. The duct must be leak-tight from the AIIR exhaust grille to the HEPA terminal and onward to atmospheric discharge. Any leak in the duct path under the negative-pressure section places a quantum of contagious air outside the duct in unsealed building voids. SBKJ specification is Type 304 stainless steel, AS 4254 Class C construction (1,500 Pa), TIG-welded longitudinal seams, gasketed and mastic-sealed transverse joints, SMACNA Seal Class A throughout, leakage tested at 1.5 times maximum operating pressure with Class 6 or better allowable leakage per AS 4254. The duct runs at negative pressure (the fan is downstream of the AIIR) so that any leak draws building air into the duct rather than discharging contagious air into the building.

HEPA placement and access

The HEPA H13 can sit at the room exhaust grille (close-coupled HEPA, replaceable from inside the room or via a side-access housing in the anteroom) or at the rooftop discharge (terminal HEPA at the discharge plenum). Close-coupled HEPA is the SBKJ preferred design pattern: the duct downstream of the HEPA carries cleaned air, the duct upstream is short (a metre or so from the room to the HEPA housing), and the HEPA bag-in/bag-out change-out can be performed by infection-control-trained maintenance staff without entering the negative-pressure room. Terminal HEPA at the rooftop discharge is acceptable but the entire duct path between the room and the HEPA is contagious, leakage-tested to higher tolerance and harder to inspect.

Exhaust discharge location

The AIIR exhaust discharges vertically upward at minimum 3 metres above the roof and minimum 8 metres horizontal from any outdoor air intake, operable window, helipad clear zone or rooftop plant intake. Minimum 12 metres per second exit velocity to ensure plume rise. The discharge location is locked at design stage with the architect, the structural engineer and the helicopter operations team (every tertiary hospital has at least one rooftop helipad clear zone that the AIIR discharge must avoid). Roof-mounted weatherhoods are inverted to prevent rain ingress without choking the discharge plume.

Protective environment isolation rooms

A protective environment (PE) isolation room is engineered to protect a profoundly immunocompromised patient from the outside world — allogeneic bone marrow transplant recipients in the first 30 to 100 days post-engraftment, severe aplastic anaemia patients, paediatric oncology patients during induction chemotherapy, severe combined immunodeficiency patients pending immune reconstitution. The PE room is the inverse of the AIIR: positive pressure with HEPA-filtered supply air sweeping the room top-down.

PE specification

Pressure: +10 Pa positive to anteroom and corridor. Supply: 12 ACH minimum through HEPA H14 terminal in a laminar ceiling array over the bed — typically a 2.4 by 1.8 metre plenum covering the head and torso of the bed. Humidity: 30 to 60 percent. Temperature: 20 to 23 degrees Celsius. Single-occupant with anteroom buffer and hand-wash basin at anteroom entry. Smooth, cleanable wall surfaces and minimum joints/seams to support cleaning regime. The anteroom is +5 Pa positive to corridor and +5 Pa positive to the patient room — the anteroom is the highest-pressure zone in the chain so that any door opening pushes filtered anteroom air into the patient room rather than corridor air. This is the inverse of the AIIR anteroom cascade.

Combined PE/AIIR rooms

A combined PE/AIIR room is engineered for the situation where a profoundly immunocompromised patient develops an airborne infection — for example a bone marrow transplant recipient diagnosed with pulmonary tuberculosis. The combined room runs anteroom positive to corridor (+5 Pa), patient room negative to anteroom (-5 Pa relative to anteroom) but the patient room still receives HEPA H14 filtered supply air. Air flows corridor → anteroom (positive) → patient room (negative) → HEPA exhaust to outdoor. The patient is protected by HEPA supply on the way in and the contagious exhaust is captured on the way out. The combined room is the most complex pressure cascade in the hospital and the most demanding to commission; SBKJ engineering practice is to add an extra layer of BMS instrumentation (separate pressure transducers on each side of the anteroom and additional logging frequency) and an extra round of smoke-pencil testing at commissioning.

The MRI suite — magnets, RF cabins and helium quench

The MRI suite is the most complex single room in the hospital from an HVAC perspective. It combines a high-field superconducting magnet, an RF-shielded Faraday cage, dedicated equipment cooling for the gradient amplifiers and the cold head compressor, and the cryogen quench discharge pipe that is the principal life-safety engineering item in the room. Every major tertiary hospital in Australia operates multiple MRI scanners (Royal Melbourne, Royal Prince Alfred, Westmead, Royal Brisbane and Women's, Royal Adelaide, Sir Charles Gairdner, Fiona Stanley and the Alfred each run between 4 and 12 MRI scanners across their imaging departments) and the design pattern applies equally to a research scanner at the Walter and Eliza Hall Institute, a clinical scanner at Mater Health, or a private imaging suite operated by Capitol Imaging or I-MED.

MRI scanner room specification

Air change rate: 6 ACH supply with manufacturer-specific cooling supplemental. Humidity: 40 to 60 percent (humidity excursion is a magnet stability risk on some scanner models). Temperature: 18 to 22 degrees Celsius. Pressure: neutral to slight positive (+0 to +5 Pa) relative to corridor and control room. The supply ductwork enters the scanner room through wave-guide or honeycomb panel penetrations matched to the Faraday cage manufacturer — the wave-guide passes air without passing RF, preserving the cage's electromagnetic isolation. The supply duct upstream of the cage is conventional galvanised; the section penetrating the cage and the diffuser inside the cage is non-ferromagnetic (304 stainless steel, aluminium or fibreglass) because any ferromagnetic component near the magnet is a projectile hazard.

Equipment room and control room

The MRI equipment room (the technical room housing the gradient amplifiers, the cold-head compressor, the RF transmitter and the power supplies) is separately conditioned with its own supply and return. Heat rejection from the gradient amplifiers and the cold-head compressor is 8 to 25 kilowatts continuous depending on scanner model. The equipment room is typically maintained at 18 to 22 degrees Celsius with 6 to 10 ACH supply, and the manufacturer's equipment ventilation diagram is the governing reference at design stage. The MRI control room (the operator workstation, the radiologist reading station, the patient observation window) is conditioned as a general clinical workspace — 6 ACH, 22 to 24 degrees Celsius, 40 to 60 percent RH.

The cryogen quench discharge pipe

Every superconducting MRI scanner stores its magnet windings in a bath of liquid helium at 4 kelvin (minus 269 degrees Celsius). The helium boils at minus 269 degrees Celsius and a typical clinical 1.5 Tesla or 3 Tesla magnet holds 1,500 to 2,000 litres of liquid helium volume. In a quench event — deliberate (an emergency stop initiated by the operator) or accidental (a magnet failure, a fault in the cold-head compressor or a building fire reaching the scanner) — the magnet rapidly loses superconductivity, the helium boils off in a runaway exothermic reaction, and the entire helium inventory vents to atmosphere through the dedicated quench discharge pipe in 30 to 90 seconds.

The quench discharge pipe is sized to manufacturer specification (typically 250 to 400 millimetres internal diameter, larger for high-field 7 Tesla research scanners and for some intra-operative MRI configurations) and routed from the scanner cryostat vent through the building envelope to atmospheric discharge above the roof. Fabrication: Type 304 stainless steel or rigid spiral-wound aluminium with welded or flanged joints. The pipe must withstand the thermal shock of cryogenic gas at minus 270 degrees Celsius (which contracts the pipe and stresses every joint) and the pressure pulse of a full quench (typically 50 to 100 kPa peak transient). Welds are TIG and inspected per the manufacturer's specification.

Routing: minimum bends, no horizontal runs longer than the manufacturer permits (typically 3 to 5 metres without an upward slope), no shared duct or chase with any other building service. The pipe must be unobstructed — debris in the pipe during a quench creates back-pressure that fails the cryostat seal and vents helium into the scanner room. The pipe is structurally supported to take the thermal contraction at cryogenic temperature and the dead weight of any condensation/ice that forms during quench.

Discharge location: minimum 3 metres above roof, minimum 8 metres horizontal from any outdoor air intake, building penetration, operable window, pedestrian path or helipad clear zone. The discharge terminates in an inverted weatherhood; signage warns of asphyxiation hazard. The hazard is real — a quench releases enough cold helium gas to displace oxygen in a several-hundred-cubic-metre volume of outside air close to the discharge. The discharge location is signed off by the project safety officer, the local fire authority and the facility infection control team.

Annual testing: pressure test of the quench pipe at 1.5 times maximum operating pressure, visual inspection of all welds and joints, confirmation that the pipe is unobstructed, confirmation that the discharge is clear of any new building work that might encroach on the 3 metre / 8 metre clearance envelope. SBKJ supplies the stainless quench pipe sections for major MRI suite projects in Australia, welded on the SB-ZF1500 stitchwelder or longitudinally welded on the SBLR-600/600A series, with mill-certified coil traceability and pressure test certificates issued per pipe section.

CT, X-ray, fluoroscopy and nuclear medicine

CT scanner rooms

CT is significantly less demanding than MRI on the HVAC side. The CT scanner generates lower heat load (the X-ray tube rejects 4 to 8 kilowatts during scan and cools between scans), there is no cryogen and no magnetic shielding, and the room volume is smaller. Specification: 6 ACH supply, +5 Pa positive to corridor, humidity 30 to 60 percent, temperature 20 to 23 degrees Celsius, lead shielding integrated into wall and floor and ceiling assemblies per the radiation physicist. HVAC duct penetrations through shielded boundaries use lead-jacketed sleeves coordinated with the radiation physicist. The CT control room is conditioned as a general clinical workspace.

X-ray and fluoroscopy

General X-ray rooms are the simplest imaging zone HVAC-wise: 6 ACH supply, +5 Pa positive, lead shielding integrated. The procedure mix is short and the room is sparsely occupied so the heat load is low. Fluoroscopy rooms run higher procedure times and may host barium swallow, voiding cystourethrogram and other longer-duration procedures — the HVAC is the same pattern as X-ray but the room may need additional cooling for the C-arm tube during extended fluoroscopy.

Nuclear medicine hot lab

The hot lab is the radio-pharmaceutical compounding zone — the room where the technologist draws up doses of Tc-99m, Ga-67, I-123, F-18-FDG (for PET) and other radio-isotopes from delivered generator output or shielded vial supply. The hot lab is engineered as a containment space: 12 ACH supply, negative pressure (-5 to -10 Pa) to corridor for one-way containment of any aerosol spill, lead-shielded fume hood with Type 304 or 304L stainless steel exhaust to outdoor terminating clear of any intake. The ARPANSA Radiation Protection Series and AS/NZS 2243.4 govern the radiation engineering controls; the HVAC scope coordinates with the radiation safety officer.

The PET scanner room is conventional CT-equivalent HVAC (6 ACH, +5 Pa, lead shielding) but the PET facility as a whole carries the additional hot-lab requirement upstream. The patient injection room (where the patient receives the radiopharmaceutical dose and waits for biodistribution) is conventionally conditioned but the room and the corridor between the injection room and the scanner room are designed to minimise unshielded exposure to staff during the patient's high-activity phase.

The day surgery and day procedure unit

Day surgery centres — standalone facilities and the day procedure units inside major hospitals — perform short-stay surgical and procedural cases under regional, general or sedation anaesthesia: ophthalmic surgery, dermatology procedures, gastroenterology endoscopy, gynaecology procedures, urology procedures, orthopaedic arthroscopy, plastic and reconstructive day cases, dental and oral surgery, and a wide range of pain management interventions. The Australian day surgery sector is consolidated under Healthscope, Ramsay Health Care, Healius Day Hospitals, Nexus Hospitals, Cura Day Hospitals, ICON Cancer Centre and a range of specialist single-site operators including Sydney Day Surgery, Box Hill Surgery and the day procedure units inside Eastern Health and Monash Health.

The day surgery HVAC specification is essentially the operating theatre pattern at the lower end of the band, governed by AS 4815 (office-based health care facilities) and AHFG HPU 590 (Day Procedure Unit) where the facility is freestanding, or by full ASHRAE 170 / AS 1668.2 / AHFG HPU 510 where the day procedure unit is inside a major hospital and shares the central HVAC plant. Specification for a Class B day procedure room: +5 to +10 Pa positive, 15 to 20 ACH supply through HEPA H13 terminal, 4 ACH outdoor air, 30 to 60 percent humidity, 20 to 23 degrees Celsius temperature.

Day surgery PACU (Stage 1 and Stage 2 recovery) operates as conventional PACU at 6 to 15 ACH, +5 Pa positive, oxygen alarm at breathing height. The day-stay discharge lounge (Stage 3) is conditioned as a general clinical waiting area. The pre-op holding bay is conventional clean with 6 ACH supply.

The recovery PACU and pre-op holding

The Post-Anaesthesia Care Unit (PACU), also called recovery, is the room where patients emerge from anaesthesia immediately post-operatively. PACU classification follows ASHRAE 170: Class B / C ventilation, +5 Pa positive to corridor, 6 to 15 ACH supply (6 ACH for general PACU bays, 15 ACH for resuscitation-grade bays and Stage 1 recovery beds in tertiary trauma centres). Humidity 30 to 60 percent. Temperature 22 to 24 degrees Celsius. Oxygen alarm at breathing height in any enclosed PACU bay — the bays carry continuous medical oxygen at the wall outlet and the Safe Work Australia upper limit of 23.5 percent enriched-oxygen atmosphere applies.

Supply is via ceiling diffuser at the head of each bay; return is at the foot. Bay-to-bay airflow is not critical the way it is in an ICU because PACU is short-stay (1 to 4 hours typical) and the principal infection control concern is from PACU back to the corridor and the OR — managed by the +5 Pa positive cascade. Many modern PACU bays are designed with full privacy partition or full wall and door per the AHFG; the HVAC design treats them as individual rooms with shared corridor return.

The pre-op holding bay (where patients are prepared for surgery immediately before transfer to the OR) is a conventional clean clinical space: +5 Pa positive, 6 ACH supply, 22 to 24 degrees Celsius. The anaesthetic induction room adjacent to each OR sits between the pre-op holding bay and the OR proper at +5 Pa positive to corridor and neutral to the OR; 15 ACH supply because the anaesthetic gas inventory in the induction room can be significant during a long induction.

Bronchoscopy and endoscopy suites

The bronchoscopy and endoscopy suite is engineered as a negative-pressure procedural envelope. Bronchoscopy in particular generates significant aerosol of patient respiratory secretions; if the patient has unsuspected airborne tuberculosis or a respiratory virus, the procedure aerosolises the pathogen across the room. The room is engineered to contain the aerosol regardless of the patient's known infectious status.

Specification: -5 to -10 Pa negative to corridor, 12 to 15 ACH supply with single-pass exhaust through HEPA H13 (no recirculation back to the building), MERV 13 supply make-up, humidity 30 to 60 percent, temperature 20 to 23 degrees Celsius. The procedure room is paired with a clean scope storage cabinet positively pressurised to the procedure room (so that aerosol from the procedure does not enter the clean scope store), with the scope reprocessing room separately conditioned to AS/NZS 4187 specifications (refer the CSSD HVAC duct guide).

The exhaust ductwork mirrors the AIIR pattern: Type 304 stainless steel, AS 4254 Class C, TIG-welded longitudinal seams, SMACNA Seal Class A, leakage tested to Class 6 or better, HEPA H13 close-coupled to the procedure room or terminal at rooftop discharge, exhaust discharge minimum 3 metres above roof and 8 metres horizontal from any intake.

The cytotoxic compounding pharmacy

The cytotoxic compounding pharmacy — sometimes called the chemotherapy compounding pharmacy or the oncology pharmacy — is where the hospital pharmacist prepares patient-specific cytotoxic chemotherapy doses for the oncology infusion units and the inpatient oncology wards. The cytotoxic agents (carboplatin, cisplatin, doxorubicin, paclitaxel, the entire monoclonal antibody portfolio, and dozens of other cytotoxic and biologic agents) are mutagenic, teratogenic and carcinogenic to staff; the engineering controls are governed by USP 800 (United States Pharmacopeia, used as the international reference), the Society of Hospital Pharmacists of Australia (SHPA) compounding guidelines, and AS/NZS 2243.3 (microbiological safety and containment) for the biological safety cabinet exhaust.

The design pattern follows the broader pharmaceutical cleanroom playbook (refer the pharmaceutical manufacturing HVAC duct guide) at hospital scale: ISO 7 anteroom at +10 Pa positive to corridor, ISO 7 buffer area at +5 Pa positive to anteroom (or +10 Pa for hazardous compounding), ISO 5 inside the biological safety cabinet (BSC), with the BSC exhaust ducted directly to outdoor through dedicated Type 304 stainless steel duct. The BSC operates at a face velocity of 0.4 to 0.5 metres per second inward at the front sash, capturing aerosol from the compounding work; the exhaust is sized to handle the BSC at full design flow plus any redundancy required by the manufacturer's certification.

The hospital-scale cytotoxic compounding pharmacy is engineered to USP 800 and to the Therapeutic Goods Administration Code of Good Manufacturing Practice for medicinal products where the facility is registered as a manufacturer. The HVAC ductwork is fabricated to AS 4254 Class B on the supply plenum (with HEPA H13 or H14 terminal in the anteroom and the buffer) and Class C on the BSC exhaust, all in 304 stainless steel with TIG-welded seams and SMACNA Seal Class A. The exhaust discharge follows the AIIR pattern: 3 metres above roof, 8 metres horizontal from any intake, 12 metres per second exit velocity.

The hyperbaric oxygen therapy chamber

The hyperbaric oxygen therapy (HBOT) chamber is engineered for the delivery of 100 percent oxygen at elevated pressure (typically 2.0 to 2.8 atmospheres absolute) to patients with carbon monoxide poisoning, decompression sickness, gas gangrene, refractory osteomyelitis and a range of other indications including some chronic wound healing and post-radiation tissue damage protocols. The chamber itself is a pressure vessel engineered under AS 1210 (pressure vessels) and is not directly an HVAC scope, but the chamber room (the technical room housing the chamber) carries an oxygen-enriched zone classification that governs the HVAC design around it.

The chamber room HVAC: 12 ACH supply, +5 Pa positive to corridor, humidity 30 to 60 percent, temperature 20 to 23 degrees Celsius. The room around the chamber is classified per AS/NZS 60079-10-1 as Zone 2 (oxygen-enriched atmosphere not normally present but may occur in abnormal operation). All electrical equipment within the Zone 2 envelope is Ex-rated; the HVAC ductwork within the Zone 2 envelope is spark-resistant aluminium per AS/NZS 60079-14, with non-sparking diffusers and dampers. The supply ductwork outside the Zone 2 envelope reverts to conventional galvanised or stainless.

Oxygen alarm at breathing height with continuous BMS logging; alarm at 23.0 percent (warning) and 23.5 percent (Safe Work Australia upper limit) for ambient oxygen enrichment. The chamber's own ventilation discharge (chamber air that the chamber operator vents during decompression) is routed through a dedicated oxygen-rated discharge to outdoor, not into the building return path. The discharge terminates clear of any ignition source and clear of any outdoor air intake. The HBOT scope is small but specialised; SBKJ supplies the spark-resistant aluminium duct sections for HBOT room installations on major hospital projects.

The burns unit

The burns unit is engineered for thermal regulation of the burns patient and for infection control. Severe burns patients lose the thermoregulatory function of their skin and require ambient temperature 25 to 30 degrees Celsius and 50 percent RH for pain control and metabolic stability. The infection control posture is towards the protective environment end of the spectrum: ISO Class 7 / 8 background, HEPA H13 supply, +5 Pa positive to corridor for individual patient rooms.

Specification: 15 ACH supply through HEPA H13 ceiling diffuser, +5 Pa positive to corridor, 25 to 30 degrees Celsius, 50 percent RH. The high ambient temperature and humidity envelope is uncomfortable for staff in regular scrubs — burns unit staff typically wear lighter-weight uniforms — and the HVAC must hold both the temperature and the humidity envelope continuously to support the patient's thermal stability.

The neonatal intensive care and special care nursery

The neonatal intensive care unit (NICU) and special care nursery accommodate critically ill newborns including extremely premature infants (born at 23 to 28 weeks gestation), term infants with congenital cardiac, respiratory or surgical conditions, and infants recovering from major neonatal surgery. The HVAC envelope is calibrated to the infant's thermoregulatory immaturity, the high air handling requirements for infants on mechanical ventilation, and the infection control posture for a population that is uniformly immune-immature.

Specification: 6 ACH supply, +5 Pa positive to corridor (some designs run neutral pressure for shared bays), 22 to 26 degrees Celsius temperature with 50 percent RH critical (the 50 percent target reduces evaporative skin water loss in the most premature infants whose skin is not yet a competent barrier), HEPA H13 supply terminal in non-aspirating ceiling diffusers. Individual bedspace airflow is gentle — the infant in an incubator does not experience the direct supply airflow, which is delivered to the bedspace volume around the incubator. The NICU specialty within paediatric tertiary hospitals (Royal Children's Melbourne, Westmead Children's, Mater Children's, Lady Cilento, Princess Margaret) is one of the most demanding HVAC zones in the hospital despite the modest ACH because the temperature and humidity envelope is so tight.

The paediatric oncology ward

Paediatric oncology wards combine the protective environment posture (immunocompromised patients during induction chemotherapy for acute lymphoblastic leukaemia, acute myeloid leukaemia, solid tumours and neuroblastoma) with the family-room design pattern of paediatric inpatient accommodation. Specification: 12 ACH supply through HEPA H14 terminal, +10 Pa positive to corridor, humidity 30 to 60 percent, temperature 20 to 23 degrees Celsius. The room volume is larger than an adult PE room because it accommodates a parent bed alongside the patient bed. The parent presence is an infection control consideration — the parent is a vector for outside-world pathogens — managed by the HEPA supply filtration and the cleaning regime rather than by isolating the parent.

The general ward and the inpatient bed accommodation

The general acute ward bed accommodates inpatients who do not require ICU, HDU, isolation or specialty care. The HVAC envelope is the simplest in the hospital but the volume of ductwork is the largest because the ward bed accommodation is the largest single floor area in any tertiary hospital.

Specification: V_p 10 litres per second per person outdoor air (AS 1668.2 reference for an acute inpatient bed), 6 ACH supply, +5 Pa positive to corridor (or neutral where corridor is the higher acuity zone), humidity 30 to 60 percent, temperature 23 to 24 degrees Celsius. Galvanised steel duct to AS 4254 Class B on the supply, conventional return path. The ductwork serves the patient bedspace at the head of each bed, with corridor supply and return at the corridor ceiling. The maternity ward, the birthing suite, the paediatric general ward, the medical ward, the surgical ward, the orthopaedic ward, the cardiology ward, the neurology ward, the rehabilitation ward and the palliative care ward all follow this pattern with minor adjustments for specialty.

The maternity unit, birthing suite and obstetric theatre

The maternity unit operates as a general acute ward with the birthing suite carrying additional specifications. The birthing suite room (where vaginal birth takes place) operates as Class A / B at +5 Pa positive, 6 to 12 ACH supply, 22 to 24 degrees Celsius, 30 to 60 percent humidity. Many birthing suites are now "same-room" configurations where the patient labours, delivers and recovers in the same room, requiring the room to support the brief delivery episode without compromising the longer labour and recovery phases.

The obstetric operating theatre — where caesarean section is performed, planned or emergency — is engineered as a full Class B / C operating theatre per the OR specifications above: 25 ACH, +10 Pa positive, HEPA H13 or H14 laminar terminal, 17 to 21 degrees Celsius for elective caesarean or 20 to 23 degrees Celsius for emergency caesarean (the temperature window adjusts to the urgency of the case and the team's thermal posture). The neonatal resuscitation area inside or adjacent to the obstetric theatre is engineered to NICU posture with the additional ambient temperature uplift for the newborn.

The emergency department, trauma bay and decontamination room

The emergency department is engineered for very high air handling capacity at high patient throughput. The ED triage and waiting area, the treatment cubicles, the resuscitation bays and the trauma bay each carry distinct HVAC specifications.

Triage and waiting

High V_p supply (15 litres per second per person under AS 1668.2 for waiting room occupancy), 6 ACH supply, +5 Pa positive to street entry and to the corridor inwards into the department. The high outdoor air component is to manage the unknown infection status of every walk-in patient.

Treatment cubicles

6 ACH supply, +5 Pa positive to corridor, conventional clinical room HVAC. Most treatment cubicles are partitioned with curtains rather than full walls, so the HVAC operates at the bay level rather than the cubicle level — the supply enters the bay through ceiling diffusers above each cubicle, the return is at high-wall grilles along the bay perimeter.

Resuscitation bay and trauma bay

The resuscitation bay (resus bay) and the trauma bay are engineered as Class B procedural rooms with surgical-grade air handling for the airway management, central line insertion, chest decompression, emergency thoracotomy and rapid stabilisation that happens there. 15 to 20 ACH supply through HEPA H13 ceiling plenum (1.8 by 1.8 metres minimum over the resus table), +5 to +10 Pa positive to corridor, 30 to 60 percent humidity, 20 to 23 degrees Celsius temperature. The trauma bay in a major trauma centre (Alfred, Royal Melbourne, Royal Brisbane and Women's, Royal Adelaide, Liverpool, Westmead, Royal Perth) sees rapid arrival of severely injured patients with unknown infection status, and the HVAC posture is correspondingly cautious — HEPA terminal and full pressure cascade documented.

Decontamination room

The ED decontamination room (for hazmat exposure, chemical contamination, radiation contamination) is engineered as a negative-pressure containment with water deluge integration. -10 Pa negative to corridor, single-pass exhaust through HEPA H13 (or activated carbon for known chemical contamination), 15 ACH minimum. The room includes a chemical shower bay and a drainage system that captures the contaminated effluent rather than discharging to sewer. The HVAC duct in the decontamination room is 304 stainless steel to resist the chemical contamination that finds its way into the exhaust path.

The mortuary, autopsy room and pathology integration

The hospital mortuary and autopsy room are engineered to negative-pressure containment with formaldehyde and tissue-aerosol management. The full design pattern is covered in the forensic pathology and coronial mortuary HVAC duct guide. The brief summary: -5 to -10 Pa negative to corridor, 12 ACH single-pass exhaust, 304 stainless steel duct on the autopsy table downdraft and the body store exhaust, formaldehyde monitoring at breathing height.

The hospital pathology laboratory adjacent to the OR suite (for intra-operative frozen section, immediate biopsy reporting, blood bank and microbiology) follows the clinical pathology design pattern covered in the clinical diagnostic pathology lab HVAC duct guide. The pathology lab carries the same fume cupboard and biosafety cabinet exhaust requirements as a standalone clinical lab.

The pharmacy, dispensary, linen handling and kitchen

Pharmacy and dispensary

The hospital pharmacy main dispensary is engineered as a clean clinical workspace: 6 ACH supply, neutral to +5 Pa positive to corridor, conventional galvanised duct. The cytotoxic compounding zone inside the pharmacy is covered above and runs at much higher specification. The unit dose dispensing area and the medication store are conventional clean clinical workspace.

Linen handling

The hospital linen handling rooms operate as clean and soiled separated airflow. The clean linen store is +5 Pa positive to corridor with 6 ACH supply; the soiled linen receipt and bagging room is -5 Pa negative to corridor with 6 to 10 ACH single-pass exhaust to outdoor through MERV 13 or HEPA filter as the infection control profile requires. The separation prevents soiled aerosol crossing into the clean linen store.

Kitchen and cafeteria

The hospital kitchen runs as a conventional commercial kitchen with the additional FSANZ Food Safety Standards posture for a food-service operation feeding clinically vulnerable patients. AS 1668.2 governs the mechanical ventilation; NFPA 96 is the international reference for cooking exhaust hood design and grease duct fabrication. The kitchen exhaust ductwork uses welded 304 stainless steel on the grease duct from the canopy hood to the rooftop discharge, with AS/NZS 1530.4 fire-rated wrap or shaft enclosure on the duct. The cafeteria is conventional commercial dining HVAC.

The public corridor, waiting and administration spaces

The hospital public spaces — main entry, corridors, waiting rooms, family rooms, administration offices, meeting rooms and clinical support workspaces — operate as conventional commercial HVAC with hospital-grade infection control posture: 6 ACH supply, neutral pressure or +5 Pa positive (depending on the relationship to the clinical zones), AS 1668.2 outdoor air rates, conventional galvanised duct. The corridor pressure relationships are the "backbone" that the perioperative and critical-care cascade relies on; the corridor must be held at the design pressure relative to every adjacent room or the cascade fails room by room.

Procurement and the Australian operator landscape

Hospital perioperative and critical-care HVAC procurement runs through two distinct channels.

The public hospital channel

Public hospitals are procured by the relevant state health infrastructure agency — Victorian Health Building Authority, NSW Health Infrastructure, Queensland Health Building Services, SA Health Infrastructure, Western Australia Department of Health Infrastructure, Australian Capital Territory Health Infrastructure, Tasmania Department of Health, Northern Territory Department of Health. Tenders are typically structured around managing contractor or design-and-construct delivery; the mechanical scope is awarded to a head mechanical contractor who in turn subcontracts the ductwork fabrication and installation. The major public hospital projects in current planning or delivery include the new Footscray Hospital (VIC), the new Royal Melbourne Hospital redevelopment, the Northern Hospital expansion (VIC), the Frankston Hospital expansion (VIC), Box Hill Hospital expansion (Eastern Health, VIC), Northern Beaches Hospital expansion (NSW), Bankstown Hospital redevelopment (NSW), Liverpool Hospital expansion (NSW), Tweed Hospital (NSW), Princess Alexandra expansion (QLD), Royal Brisbane and Women's expansion (QLD), Gold Coast University Hospital expansion (QLD), Sunshine Coast University Hospital expansion (QLD), Royal Adelaide Hospital ongoing (SA), Fiona Stanley Hospital expansion (WA), the Perth Children's Hospital ongoing operational support, Canberra Hospital expansion (ACT) and the Royal Hobart Hospital redevelopment (TAS).

The principal Australian health networks operating the hospitals are NSW Health (15 Local Health Districts including Sydney, Western Sydney, South Eastern Sydney, South Western Sydney, Northern Sydney, Western NSW, Far West, Mid North Coast, Hunter New England, Illawarra Shoalhaven, Murrumbidgee, Nepean Blue Mountains, Northern NSW, Southern NSW and Sydney Local Health District), Victoria Department of Health (multiple health services including Alfred, Austin, Eastern, Northern, Peninsula, Monash, Royal Melbourne, St Vincent's and Western), Queensland Health (16 Hospital and Health Services including Metro North, Metro South, Children's, Gold Coast, Sunshine Coast, West Moreton, Darling Downs, Central Queensland, Mackay, Townsville, Cairns and Hinterland, Wide Bay, South West, Central West, North West, and Torres and Cape), SA Health (multiple Local Health Networks), WA Health (multiple Health Service Providers including North Metro, South Metro, East Metro and WA Country Health Service), ACT Health, Tasmania Health and Northern Territory Health.

The private hospital channel

Private hospital procurement runs through the corporate property and capital works teams at Ramsay Health Care (ASX:RHC — the largest private hospital operator globally with significant Australian operations), Healthscope (Brookfield-owned — the largest private hospital operator headquartered in Australia), Calvary Health Care (Catholic order — multiple sites), Mater Health Services (Catholic order — Brisbane, Newcastle, Sydney), St John of God Health Care (Catholic order, predominantly Western Australia and Victoria), Cabrini Health (Catholic order, Victoria), Epworth HealthCare (Victoria) and Genesis Care (cancer specialty). Procurement is typically tighter in scope than the public tendered process and decisions are often centralised at the corporate level for multi-site rollouts.

The major engineering consultants servicing both channels are Aurecon (multidisciplinary, healthcare specialist), Norman Disney + Young (NDY, Tetra Tech-owned, healthcare specialist), WSP Australia, Arup, Lendlease (project management on PPP work), John Holland (health infrastructure delivery), Capella Capital (PPP healthcare), Plenary Group (PPP healthcare including the Royal Adelaide PPP) and Healthcare Infrastructure VIC (the Royal Children's Hospital PPP and the Monash PPP). The industry bodies driving design knowledge are the AHIA Australasian Health Infrastructure Alliance, the ACSQHC Australian Commission on Safety and Quality in Healthcare, the AHIA Asia Pacific Healthcare Architects Association and the IHEA Institute of Healthcare Engineering Australia with its NSW, VIC and QLD chapters running the annual conferences and CPD programs that drive working knowledge of perioperative HVAC.

SBKJ's role across both channels

SBKJ supplies the auto duct production lines that fabricate the ductwork for hospital perioperative and critical-care projects in both channels. The standard perioperative configuration is the SBAL-V running Type 304 stainless coil for the OR supply plenum, the AGSS exhaust, the cath lab supply plenum, the AIIR exhaust, the cytotoxic BSC exhaust and the MRI quench discharge sections, switching to galvanised for the bulk return and corridor scope, all within a single shift with a documented changeover sequence. The TDF flanging operation runs the same on both coil types, accepts mastic and butyl sealant for HEPA-grade integrity, and handles laminar flow plenum fabrication to dimensional tolerance.

The SBAL-V auto duct line specifications: 16 metres per minute working speed, 87 kilowatt installed power, 0.5 to 1.5 millimetre coil thickness, 1,250 or 1,500 millimetre maximum coil width, 380V / 50Hz / 3PH supply, 16 ton machine weight. The SB-ZF1500 automatic stitchwelder for welded longitudinal seams on stainless plenums, AGSS exhausts and MRI quench-discharge sections: 0.8 to 3 millimetre material thickness, 100 to 1,500 millimetre length capacity, 150 to 1,500 millimetre diameter range, 2,500 by 1,000 by 2,350 millimetre footprint, 380V / 50Hz / 3PH supply. The SBSF-1525 round tube flanging machine for cleanroom round duct ends: 2.5 kilowatt, 520 kilogram, 2,200 by 1,100 by 1,240 millimetre footprint, 380V / 50Hz / 3PH supply.

SBKJ engineers in our Box Hill North Victoria office provide design and fabrication support throughout the project lifecycle with a 12-hour reply commitment to spec questions — from a senior engineer, not a salesperson. Our customers are the mechanical contractors and fabricators producing ductwork for hospital perioperative scopes nationally; we are upstream of the project tender, supplying the production capability that makes the project deliverable on programme and on the precise material specification the hospital requires.

Commissioning — the binder that the hospital lives with

The commissioning binder is the single most important document the hospital receives at handover. Every future NSQHS accreditation cycle, ACSQHC review, AHFG audit, IHEA-led engineering inspection and infection control review will start with the commissioning binder as the baseline against which current performance is compared. SBKJ engineering practice is to participate in the commissioning binder structure at design stage so that the ductwork fabricator's deliverables map cleanly into the binder.

The binder for a perioperative and critical-care HVAC handover comprises the following sections:

• Duct leakage test reports — SMACNA / AS 4254 leakage test logs per duct section, signed by the commissioning engineer and counter-signed by the mechanical consultant. Test pressure 1.5 times maximum operating pressure; allowable leakage Class 6 or better for AS 4254 Class C exhausts.
• Pressure relationship test logs — cascade boundary by cascade boundary, smoke-pencil test logs documenting airflow direction at door-closed and door-open conditions, time-to-equilibrium after door operation.
• ACH verification logs — supply and return airflow measurement at every diffuser and grille in every classified zone, cross-checked against design.
• HEPA integrity certificates — PAO / photometer test results per IEST-RP-CC034 for every HEPA H13 and H14 in the precinct, with the certificate identifying the filter serial number, the test pressure, the upstream challenge concentration and the maximum downstream penetration.
• ISO 14644 particle count reports — commissioning particle counts per zone for every ISO-classified room (OR, cytotoxic anteroom, cytotoxic buffer, PE room) measured at-rest per ISO 14644-1.
• Laminar field smoke-pencil test logs — for each OR, documenting the downward velocity profile across the plenum face and the lateral airflow at the perimeter of the laminar field.
• Temperature and humidity baseline logs — commissioning week temperature and humidity in every classified zone, hour-by-hour, against design.
• BMS point list with alarm verification — every BMS sensor identified, every alarm threshold set, every alarm tested at commissioning.
• Gas vapour monitor calibration certificates — AGSS performance test logs, oxygen monitor calibration, nitrous oxide and volatile anaesthetic monitor calibration where fitted.
• MRI quench discharge pressure test — pressure test of the quench pipe at 1.5 times design pressure, visual inspection of welds, confirmation of clear discharge path.
• NSQHS clinical quality file integration — cross-reference of the commissioning binder to the organisation's NSQHS evidence portfolio for Standard 3 (preventing and controlling healthcare-associated infections).
• AHFG room-by-room compliance matrix — a sign-off that every room as built matches the AHFG HPU specification it was briefed against.
• ACSQHC accreditation linkage — identification of the next ACSQHC accreditation cycle date and the binder sections that will support it.

The binder is reissued annually with re-test results for HEPA integrity, particle counts, pressure cascade and BMS alarm verification. The annual re-test cycle is the engineering control that keeps the hospital inside ASHRAE 170 and AHFG continuously rather than once at handover.

Conclusion — designing for thirty-year clinical performance

An Australian hospital perioperative and critical-care precinct is a 30-year clinical investment. The HVAC ductwork installed today will still be moving air, holding pressure cascade, filtering through HEPA terminals and scavenging anaesthetic gas when the current clinical team has long retired, when the surgical techniques have changed twice, when the implant and device portfolio is unrecognisable, and when the patient cohort the precinct was briefed for has moved on to a new generation of disease and care expectations. Designing the HVAC against ASHRAE 170-2021, AHFG, AS 1668.2, AS 4254 and the broader Australian standards stack — with Type 304 stainless steel in the surgical and isolation envelope, HEPA H13 / H14 at every terminal supply, continuous BMS monitoring of pressure cascade, temperature, humidity and gas vapour, robust commissioning and annual re-verification — costs more than a generic ducted HVAC scope at first install and pays for itself many times over the precinct lifetime in reduced surgical site infection, sustained NSQHS accreditation through every cycle, lower lifecycle replacement cost, and continuous availability of every operating theatre, every cath lab, every ICU bedspace and every MRI scanner to the hospital's clinical mission.

The Australian healthcare sector is consolidating under the major public networks operating through state health infrastructure agencies, the private hospital networks led by Ramsay Health Care, Healthscope, St Vincent's, Mater, Calvary, St John of God, Cabrini, Epworth and Genesis Care, and the specialist day-surgery, oncology and cardiac segments operating across both. SBKJ supplies the auto duct production lines that fabricate the ductwork for these facilities. The SBAL-V is configured for Type 304 stainless work on the surgical, isolation and chemical-vapour envelope; the SB-ZF1500 stitchwelder handles the laminar plenum welded seams, the AGSS exhausts, the AIIR single-pass duct and the MRI cryogen quench discharge sections; the SBSF-1525 handles round duct flanging on cleanroom supply; the SBFB-1500 handles spiral return riser fabrication; the SBPC1500 handles plasma cutting on stainless; the SBLR-600 longitudinal welders complete the welded stainless components. Our engineering team in Box Hill North Victoria is available to support fit-out contractors, mechanical consultants and hospital property teams throughout the design and fabrication cycle.

Whether your project is a new-build major teaching hospital perioperative precinct at Royal Melbourne, Royal Prince Alfred, Westmead, Royal Brisbane and Women's, Royal Adelaide, Sir Charles Gairdner, Fiona Stanley or Canberra scale; a private hospital cardiac or oncology surgical wing inside Ramsay, Healthscope, St Vincent's, Mater, Calvary, St John of God, Cabrini, Epworth or Genesis Care; a day surgery facility under AS 4815; a major hybrid OR retrofit; an MRI suite extension; an ICU expansion; an AIIR / PE conversion; or a refurbishment of an existing precinct to current standards — the engineering principles are the same, ASHRAE 170 and AHFG are non-negotiable, AS 1668.2 and AS 4254 form the legal floor, and the room-by-room design patterns set out in this guide are the SBKJ engineering team's recommended starting point.

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FAQ

What pressure differential is required between an operating theatre and the surrounding corridor?

ASHRAE 170-2021 and AHFG require a general operating theatre to be held at positive pressure relative to corridor, anaesthetic induction, sterile core and dirty utility. SBKJ engineering practice targets +5 to +10 Pa for general OR and +10 to +15 Pa for orthopaedic, cardiac and neurosurgical theatres with continuous BMS monitoring, door-side visual indicators and alarming at 50 percent of design as warning and 25 percent as critical.

What air change rate is required in an operating theatre?

ASHRAE 170-2021 requires 20 ACH minimum supply with 4 ACH minimum outdoor air. SBKJ engineering practice is to size at 25 ACH for general OR and 25 to 30 ACH for orthopaedic and cardiac OR, delivered through a 2.4 by 2.4 metre (general) or 3.0 by 3.0 metre (orthopaedic and cardiac) laminar HEPA terminal ceiling plenum over the surgical table, with four-corner low wall return at floor level.

What HEPA filtration grade is required at the operating theatre ceiling?

HEPA H13 minimum at the terminal supply per ASHRAE 170 and AHFG. SBKJ engineering practice is HEPA H14 (per ISO 29463) at the laminar plenum for orthopaedic, cardiac, neuro and implant surgery, achieving ISO Class 5 directly under the laminar field. Every HEPA tested at commissioning per IEST-RP-CC034 (PAO challenge upstream, photometer scan downstream); acceptance no penetration above 0.01 percent.

What ductwork material is required in an operating theatre or cath lab?

Type 304 stainless steel for the OR supply plenum, the laminar ceiling array, the AGSS anaesthetic gas scavenging exhaust, the cath lab supply plenum, the cytotoxic BSC exhaust, the AIIR single-pass exhaust and the MRI quench discharge sections. Galvanised steel to AS 4254 G90 in the bulk return and corridor scope. All perioperative ductwork fabricated to SMACNA Seal Class A and leakage tested before insulation per AS 4254 Class B or Class C as applicable.

How is anaesthetic gas waste handled in HVAC?

Waste anaesthetic gas (nitrous oxide and volatile halogenated agents) is routed from the AGSS receiving unit on each anaesthetic machine through dedicated 304 stainless steel duct to outdoor per AS 4032.1. Safe Work Australia WES: nitrous oxide 25 ppm 8-hour TWA, isoflurane 50 ppm, sevoflurane 50 ppm, desflurane 50 ppm. Exhaust discharges minimum 3 metres above roof, 8 metres horizontal from any intake, 12 metres per second exit velocity, with N+1 backup fan.

What ventilation is required for an airborne infection isolation room?

-5 to -10 Pa negative to anteroom and corridor (ASHRAE 170 minimum -2.5 Pa). 12 ACH single-pass exhaust through HEPA H13. Anteroom +5 Pa to AIIR and neutral to corridor as air-lock. Door-side pressure indicators and BMS alarming on cascade loss. Exhaust discharge minimum 3 metres above roof and 8 metres horizontal from any intake.

What ventilation is required for a protective environment isolation room?

+10 Pa positive to anteroom and corridor. 12 ACH supply through HEPA H14 laminar ceiling array over the bed. Humidity 30 to 60 percent. Temperature 20 to 23 degrees Celsius. Anteroom buffer with hand-wash basin. Combined PE/AIIR rooms run anteroom-positive to corridor, patient room negative to anteroom with HEPA exhaust.

What does the MRI cryogen quench discharge pipe do and how is it sized?

Routes helium from the MRI cryostat to atmospheric discharge in a quench event. Typically 250 to 400 millimetres diameter per manufacturer specification, 304 stainless steel or rigid spiral-wound aluminium with welded or flanged joints. Terminates in an inverted weatherhood minimum 3 metres above roof, safe distance from any intake or pedestrian path, with asphyxiation signage. Pressure tested annually.

What ventilation is required for a hybrid OR with intra-operative imaging?

Same surgical-grade airflow as a standalone OR (25 ACH minimum supply through HEPA H14 laminar ceiling plenum 3.0 by 3.0 metre minimum over the table, +10 to +15 Pa positive, 30 to 60 percent humidity, 17 to 21 degrees Celsius for cardiac and orthopaedic) plus dedicated cooling for the imaging equipment (8 to 15 kilowatts continuous for fixed C-arm, 40 to 70 kilowatts continuous for intra-operative MRI). Plenum cut-out coordinated with imaging equipment installer at design stage.

Which SBKJ machine produces ductwork for operating theatre and ICU specifications?

The SBAL-V auto duct line (16 m/min, 87 kW, 0.5 to 1.5 mm coil, 1,500 mm coil width) configured for Type 304 stainless with mill certificate traceability is the SBKJ flagship for perioperative HVAC. The SB-ZF1500 automatic stitchwelder (0.8 to 3 mm thickness, 100 to 1,500 mm length, 150 to 1,500 mm diameter, 380V / 50Hz / 3PH) produces welded laminar plenum boxes, AGSS exhausts, AIIR exhaust ducts and MRI quench-discharge sections. The SBSF-1525 round tube flanging machine (2.5 kW, 520 kg, 2,200 by 1,100 by 1,240 mm) flanges cleanroom round duct ends. The SBFB-1500 spiral former (7.5 kW, 1.20 m/min) produces theatre suite return risers. Plasma cutting on stainless uses the SBPC1500. Welded stainless components are completed on SBLR-600/600A series longitudinal welders. Spark-resistant aluminium for the hyperbaric Zone 2 envelope is the only specialty material outside the 304 / galvanised mix.