Why correctional ductwork is its own discipline
A correctional facility is a building type that compresses three of the most demanding HVAC briefs in commercial construction into one envelope. It contains a high-density residential occupancy that runs 24 hours a day, every day of the year. It contains a healthcare environment subject to the same ventilation standards used by standalone hospitals. It contains an industrial-scale kitchen, laundry and workshop block, with the same fire, grease and humidity loads found in any large institutional caterer. And it adds two requirements that no other building type imposes: anti-contraband construction across every duct run accessible to detained persons, and a duty-of-care continuity obligation that rules out single-fan ventilation outages anywhere occupied cells are present.
The result is a building where the ductwork is part of the security envelope. A 96 mm gap in a return air path is a smuggling vector. A 50 mm acoustic leak through a perimeter wall is a communication channel. A 12-hour ventilation failure in segregation is a duty-of-care incident. Mechanical engineers who design correctional facilities work shoulder to shoulder with custodial operations and counter-terrorism advisors, and the document pack at handover is countersigned by the operator before the project is accepted.
This guide is written from the SBKJ Group engineering perspective — the firm has supplied the auto duct line, spiral tubeformer and TDF flange machinery used in correctional, defence and healthcare projects across 100+ countries — and is intended to give project mechanical leads, custodial operations managers and head contractors a single authoritative reference for the ductwork specification. It covers the public standards that apply, the operator-specific overlays that apply on top, the security ductwork rules that turn the duct system into a contraband barrier, and the major Australian correctional projects in pipeline through 2030.
The standards stack — public, operator and international
Australian correctional facility HVAC sits on a stack of three layers of design rules. The public standards are the floor, the operator manuals are the working brief, and international precedent fills the gaps where Australian guidance is silent.
ASHRAE Applications Handbook Chapter 9 — institutional
Chapter 9 of the ASHRAE Applications Handbook covers educational, public assembly and institutional facilities, and is the single most useful baseline document for correctional design. The chapter tabulates indoor design conditions, ventilation rates, filtration class, pressure relationships and noise limits for cells, day rooms, dining, kitchen, laundry, visit, intake and infirmary spaces, and explicitly addresses the engineering constraints unique to correctional facilities — high occupancy density, around-the-clock operation, security envelope continuity and the contraband concealment risk inherent in any concealed duct run. Where AS 1668.2 sets a code-minimum outdoor air rate, Chapter 9 provides the engineering judgement on appropriate uplift, and the most recent revision incorporates lessons from the COVID-19 era on respiratory isolation in correctional infirmaries.
AS 1668.2 — Australian outdoor air rates
AS 1668.2 is the Australian and New Zealand standard governing mechanical ventilation in buildings, and sets the floor on outdoor air for correctional projects. The standard tabulates outdoor air rate per occupant by occupancy type — office at 10 L/s per person, dining at 7.5 L/s per person plus 0.5 L/s per square metre, kitchens at 1.0 L/s per square metre minimum plus cooking exhaust offset. Correctional cells are not a tabulated occupancy and are addressed by reference to high-density residential or by the operator manual, with most operators choosing a rate equivalent to or exceeding office occupancy plus a safety margin for body odour, smoking heritage and prolonged dwell time.
AS 1668.2 also sets the discharge separation rules that govern where kitchen, laundry and infirmary exhaust can be released — at least 6 m clear of any air intake on the same building, and 10 m or a tall discharge stack where infectious or contaminated air is discharged. These rules drive the rooftop layout on every correctional project: the kitchen, laundry and infirmary isolation exhaust stacks and perimeter AHU intakes have to be coordinated against the AS 1668.2 separation grid before the structural roof design is locked.
AS 4072.1 — Class C secure construction
AS 4072.1 is the Australian standard for components for the protection of openings in fire-resistant separating elements. Class C is the highest acoustic and physical separation grade, specified at every duct penetration through a perimeter wall in a correctional facility — sealed-seam ductwork, welded or fully gasketed frames, no removable panels on the secure side, and verification by witnessed test on the as-built duct. Class C also applies at the envelope of any segregation unit, infirmary isolation suite, intake holding area or transfer corridor where acoustic separation is part of the security brief. The corrections operator countersigns the AS 4072.1 Class C completion certificate alongside the structural and fire engineer.
ACA standards as international precedent
The American Correctional Association (ACA) Standards for Adult Correctional Institutions are the most widely cited international precedent for correctional facility design. Australian operators do not adopt the ACA standards directly, but where public Australian standards are silent the ACA tabulations on cell air supply, day room ACH, segregation pressure relationships and infirmary respiratory isolation are routinely cited in operator manuals. The security ductwork rules — the 96 mm contraband threshold, the 6 mm steel mesh specification, the tamper-resistant fastener requirement — all trace back to the ACA reference design refined across forty years of US correctional construction. For juvenile detention the ACA Standards for Juvenile Detention Facilities apply with modifications, with the same contraband ductwork rules but a higher proportion of air handling capacity directed to program and recreation spaces.
State Department of Justice and Corrective Services manuals
Each state and territory operator publishes a facility design manual that overlays the public standards. The WA Department of Justice publishes a Custodial Infrastructure Design Standard covering Casuarina, Banksia Hill, Bandyup, Hakea, Acacia and others. NSW Corrective Services publishes a Capital Works Design Standard covering Long Bay, Junee, Goulburn, Lithgow and the Special Purpose Centre. Corrections Victoria publishes a Custodial Asset Management Plan covering Western Plains, Barwon, Loddon, Dame Phyllis Frost and Ravenhall. Queensland Department of Justice publishes design guidance for Capricornia, Borallon, Maryborough and Brisbane Women's. Each manual carries detail above the public standards on cell ACH, mesh specification, fastener requirements, infirmary integration and kitchen exhaust scale, and the manuals are confidential — project teams sign NDAs before receiving them. The mechanical specification on a correctional project is the union of all three layers.
Cell block ductwork — the contraband barrier
Cell block ductwork is where the security ductwork specification is most concentrated. A typical Australian correctional facility runs 60 to 600 cells per accommodation building, arranged in single or double-bunked configurations along access landings, with day rooms, dining and program space at the ground level. The ductwork serving those cells has to deliver the design ventilation rate, sustain the design pressure cascade, refuse to host any contraband concealment voids, and survive deliberate tampering by occupants.
Air change rate by cell type
Australian correctional cells are designed for between 6 and 12 air changes per hour. The lower end of the band is appropriate for protective custody, low-security dormitory and staff accommodation. The upper end is specified for maximum security, segregation, mental health observation and any cell where the occupant is locked in for longer than 16 hours per day. The design figure is calculated against actual cell volume — typically 18 to 25 cubic metres for a single-bunk cell and 25 to 35 cubic metres for a double-bunk — with supply duct sized to deliver the flow with adequate static pressure margin for filter loading. Outdoor air content typically uplifts from the AS 1668.2 floor of 10 L/s per occupant to 12 to 15 L/s per occupant, offsetting body odour, residual smoking heritage and the long dwell time. Recirculated flow is filtered to MERV 13 or equivalent F7 grade, with the pressure cascade established between cell, landing, day room and corridor by careful balancing of supply and return.
The 96 mm contraband threshold
The single most important security ductwork rule is the 96 mm contraband threshold. No duct opening, grille, register or accessible duct run on the cell-block side may have any clear opening larger than 96 mm in any single dimension without security mesh. The figure derives from long-running ACA reference work on contraband concealment, calibrated to refuse passage of small contraband — synthetic phones, weapons, narcotics packages — observed in correctional incident reports across forty years of operations. Australian operators adopt the 96 mm figure or a tighter equivalent in their internal manuals.
The mesh specification is 6 mm woven steel, welded or pinned to the duct frame at every accessible opening, on both supply and return — and on the return is the more critical, because that is the path along which contraband is concealed for transfer. Six mm woven steel resists hand tooling, is too tight for finger purchase, and refuses passage of even the smallest contraband. The mesh frame is welded into the duct, not bolted, and any required maintenance access uses welded-frame pop-out panels with one-way fasteners on the secure side.
Smooth-interior, sealed-seam construction
Anti-contraband design extends inside the duct, where internal voids are concealment risks. The cell-block ductwork specification requires smooth-interior construction with no internal liners, no flanged crosspieces accessible from inside, and no horizontal plenums longer than 1,500 mm without an inspection port. Sealed-seam construction is mandatory — the duct is built on a sealed-seam machine such as the SBKJ SBAL-V auto duct line, with longitudinal seam sealed to AS/NZS 4254 Class A leak rating, and every transverse joint sealed with TDF flange or a welded butt-strap. Sealed-seam construction also resists physical attack: a folded Pittsburgh seam can be opened with hand tools, a welded or sealed seam cannot. The mechanical specification on a correctional project routinely calls for either a welded longitudinal seam or a Pittsburgh seam reinforced with adhesive sealant and a clinch lock — the latter is what the SBAL-V produces as standard.
Tamper-resistant grilles and registers
The grille on a cell wall is the most accessible part of the ductwork. Standard commercial grilles are removable with a screwdriver — cell-block grilles are not. The specification calls for one-way security fasteners (Torx Plus security pin, hex pin, snake-eye, three-wing or proprietary one-way patterns are all acceptable), with the fastener inventory held by the maintenance crew, not the occupants. Some operators specify welded-frame grilles with no removable face at all, with maintenance access via a hatch on the corridor side rather than the cell side. Grille face geometry is also constrained: a 600 mm by 200 mm grille face has a 200 mm clear dimension which exceeds the 96 mm rule, so the security mesh must be present behind the face — welded or riveted to the frame, the face fixed to the frame with one-way pins, and the assembly welded or bolted into the wall opening with a security perimeter.
Pressurised cells and the pressure cascade
The pressure cascade in a cell block controls transfer of odour, airborne pathogens, smoke and contraband fumes. The corridor or central spine is the pressure reference, held positive to the cells by 5 to 15 Pascals. Cells are negative to the corridor by design, so air leaks from corridor into cell rather than the reverse — useful for odour control and infectious case isolation. Day rooms are neutral or slightly positive, dining at neutral, and the kitchen strongly negative as required by AS 1668.2. Segregation cells run a two-stage cascade: the segregation envelope is held negative to the segregation corridor, which is itself held negative to the rest of the building, containing airborne and odour transfer at the envelope boundary. The cascade is verified at commissioning by manometer reading at every boundary, recorded in the commissioning pack, and countersigned by the operator before handover.
High-security visitor rooms and intake
The visitor centre is the riskiest non-secure zone in any correctional facility. Visitors arrive with contraband concealed in clothing, body cavities and personal effects, and the visit booth or contact-visit room is the primary transfer opportunity. Mechanical design contributes to the security envelope by isolating the visitor centre from the secure perimeter air handling system, by pressurising the visit booth in a controlled cascade, and by integrating thermal and trace detection within the return air path.
Separate AHU on the visitor centre
The visitor centre runs on a dedicated air handling unit isolated from the perimeter system. There is no shared return duct, no shared supply trunk and no air recirculation between the visitor centre and the cell blocks. The visitor centre AHU draws outdoor air through a filtration train including HEPA on the supply, supplies the booth and visit area, and discharges through filtration before exhaust. A fault in the visitor centre cannot propagate into the secure perimeter. The visit booth itself is pressurised positive relative to the visitor side and negative relative to the inmate side, so contraband suspended in air or vapour transfers from inmate to visitor in detection-friendly direction, with a controlled purge cycle on the BMS between visits.
Intake and reception
Intake and reception holding cells are short-dwell, high-throughput zones where new arrivals are processed before assignment. The HVAC brief is similar to a hospital triage area — high outdoor air, MERV 13 minimum filtration, negative pressure relative to the staff zone, exhaust path that does not communicate with the rest of the building, 6 to 12 ACH with the upper end appropriate for medical screening. Detained persons in intake have not yet been searched and may carry contraband or infectious load, so the intake ductwork follows the same anti-contraband rules as cell block ductwork — 96 mm threshold, 6 mm mesh, sealed-seam, tamper-resistant grilles — with thermal anomaly sensors on the return and ion mobility detection points at the exhaust diffuser.
Drug detection integrated with HVAC
Modern correctional facilities integrate drug detection sensors into the HVAC return air path. Thermal anomaly sensors detect heat signatures consistent with concealed electronics or chemical reactions. Ion mobility spectrometry sample ports sniff the return air for trace narcotics and explosive compounds. CO2 trend monitoring identifies cells with anomalous metabolic activity. The detection system runs on its own data path to the security control room, not on the BMS, but the air sampling and the ductwork that delivers it is mechanically engineered into the return run — sample ports upstream of any filter that would scrub the trace, thermal sensor housings integrated into the return diffuser frame, CO2 sensors in the return rather than the supply. The duct becomes an active security layer, not a passive air conduit.
Kitchen exhaust at scale
A correctional facility kitchen serves three meals per day to every inmate, every day of the year, with no closure for public holidays or weekends. A 1,500-bed facility runs 4,500 meals per day, and a 3,000-bed multi-precinct facility runs 9,000 meals per day. The cooking equipment scale is therefore equivalent to a large institutional caterer or a substantial banquet kitchen running multiple sittings — bratt pans, combi ovens, tilting kettles, deep fryers, range tops and bain-marie at industrial scale. The exhaust load follows.
Type 1 grease ductwork
Cooking exhaust runs in Type 1 grease ductwork specified to AS 1530 Part 4 fire resistance, AS 1668.2 air movement and the operator's grease management standard. Type 1 duct is sealed-seam stainless 316 or aluminised steel, internally smooth to allow grease cleaning, with welded transverse joints. Internal velocity is held above 7.5 m/s on the up-leg and 5 m/s on horizontal runs to prevent grease drop-out, with access doors at every change of direction. The duct is built on a sealed-seam machine — the SBKJ SBAL-V in stainless option produces sealed-seam Class A duct accepting 1.0 to 1.6 mm stainless 316 coil — and welded at every transverse joint by a qualified stainless welder, with the welds inspected to AS 1554. The riser through non-cooking floors typically carries an FRL of 120/120/120 or 240/240/240.
Hood selection and exhaust flow
Hoods are selected by cooking equipment: heavy duty (Type 1 with grease filter) over deep fryers, bratt pans and range tops at 1.5 m³/s per linear metre; medium duty over combi ovens and steamers at 1.0 m³/s per metre; light duty over warmers and bain-marie at 0.5 m³/s per metre. For a 1,500-bed kitchen the total exhaust load is 4 to 8 m³/s on a single Type 1 riser plus 1 to 2 m³/s on a separate Type 2 riser handling steam and odour from boiling and washing. Make-up air is delivered through a separate tempered AHU drawing outdoor air, conditioned to within 5 K of the kitchen target and supplied through the cooking line perimeter, with the kitchen held strongly negative to the dining and serving area to prevent grease and odour transfer.
Fire suppression and clean-out access
Type 1 grease duct carries a wet chemical fire suppression system within the hood and the riser, activated by the BMS or by a fusible link mechanical trigger. The duct is fire-rated and the riser carries a fire damper at every floor crossing. Clean-out access is provided at the base of the riser and at every change of direction, with the cleaning programme running at intervals from 4 weeks (heavy duty) to 12 weeks (light duty). For correctional facilities the cleaning crew is escorted by custodial staff because the kitchen is staffed by inmates and the riser passes through the secure envelope. Cleaning access is on the kitchen side of the perimeter, with the riser routed up through a service shaft segregated from any inmate-accessible zone, the shaft held positive to the kitchen and negative to the rooftop.
Laundry exhaust — heat, lint and antimicrobial chemistry
The correctional facility laundry handles bedding, clothing, towels and kitchen linen for the entire population, plus bedding from the infirmary which carries an additional infection control overlay. A 1,500-bed facility laundry processes around 2 to 3 tonnes of dry weight per day across washers, tumble dryers, finishing presses and folding tables. The exhaust load combines high humidity from the dryers, lint from the finishing line, residual chlorine vapour from the wash chemistry and antimicrobial agents from the bleach and oxidiser cycle.
Material and seam specification
Laundry exhaust ductwork is built in stainless steel 304 with sealed seams. Galvanized steel does not survive long-term exposure to chlorine vapour and the wash bleach atmosphere. Stainless 316 is appropriate where the wash chemistry is aggressive — particularly at infirmary linen handling and at any precinct using chlorine dioxide for biological decontamination. The seam specification is sealed Class A — the SBAL-V auto duct line produces this in stainless option in a single pass, with the duct accepting integral stiffening and no internal voids.
Tumble dryer exhaust is a special case. The exhaust air carries lint at concentrations that can build up in long horizontal runs and create a fire hazard. The duct is therefore designed for high velocity (above 8 m/s), kept short, and equipped with a lint trap upstream of the fan. The lint trap is a removable cassette with a 1 mm or 2 mm stainless mesh element, accessible from outside the secure perimeter through a service door, and inspected daily. The fan is a backdraft-isolated centrifugal with smooth impeller and stainless casing.
Discharge separation
Laundry discharge is high humidity, often at saturation, and visibly steamy at the discharge. AS 1668.2 separation rules require the discharge to be at least 6 m clear of any air intake and at least 3 m above any roof level walkway. The discharge is typically routed to a common laundry stack with a weather cap and a continuous condensate drain, with the stack height engineered to clear any rooftop penthouse. For multi-precinct facilities the laundry stack may be shared across multiple operating zones, with backflow dampers preventing recirculation between zones.
The infirmary linen handling laundry — a separate zone within the laundry building — has its own exhaust on a dedicated stack. The infirmary linen exhaust handles potentially infectious material and is filtered to HEPA before discharge. The exhaust runs negative relative to the rest of the laundry, preventing air migration from the infectious zone into the general wash area, and the pressure cascade is verified at commissioning and re-verified annually.
Infirmary integration — ASHRAE 170, BSL/PC-2 and respiratory isolation
Every Australian correctional facility includes an infirmary providing primary care, dental services, mental health support and short-stay inpatient capability. Larger precincts include an in-patient ward, a procedure room and respiratory isolation cells for infectious cases — particularly tuberculosis, which is over-represented in correctional populations globally. The infirmary is a healthcare facility and inherits the ventilation standards used in standalone hospitals.
ASHRAE Standard 170 application
ASHRAE Standard 170 is the US standard for ventilation of healthcare facilities and the most widely applied international reference for hospital and infirmary HVAC. The standard tabulates ACH, pressure relationship, filtration class and humidity range by space type — examination rooms at 6 ACH neutral, MERV 7; procedure rooms at 15 ACH positive, MERV 13; operating rooms at 20 ACH positive with HEPA at supply; respiratory isolation at 12 ACH negative, MERV 14 on return, HEPA at exhaust before atmospheric discharge. The Australian equivalent is the Australasian Health Facility Guidelines supplemented by state Department of Health design standards, but for correctional infirmaries the design typically follows ASHRAE 170 directly because operators and contractors are familiar with it from healthcare projects. The infirmary is therefore a healthcare zone embedded in a custodial envelope, with dual stack — ASHRAE 170 for healthcare, AS 4072.1 Class C for the secure perimeter, operator manual on top.
Respiratory isolation cells
Respiratory isolation cells — the airborne infection isolation rooms in ASHRAE 170 terminology — are the most demanding mechanical zone in any correctional facility. The room runs at 12 ACH minimum, negative pressure relative to the anteroom by 2.5 Pascals minimum, all exhaust direct to atmosphere through HEPA filtration with no recirculation, sealed envelope including the door, and an anteroom positive to both the room and the corridor to maintain the cascade during door openings. Supply is sealed-seam galvanized or stainless with welded transverse joints; exhaust is stainless 316 with welded transverse joints, sized for design flow and rated for HEPA pressure drop. The HEPA housing is bag-in bag-out, accessible from outside the secure perimeter through a maintenance corridor, and the exhaust stack discharges at least 10 m clear of any intake on the same building.
BSL-2 / PC-2 procedure rooms
BSL-2 and PC-2 procedure rooms handle clinical samples for diagnostics — blood, sputum, urine. The Australian standard is AS/NZS 2243.3, which sets containment, ventilation, biosafety cabinet and access requirements. PC-2 rooms run negative to the surrounding corridor, exhaust through HEPA, and the biosafety cabinet exhaust ducts to the building exhaust through a flexible duct with backdraft damper preventing reverse flow when the cabinet is shut down. The cabinet is service-accessible from outside the procedure room, allowing filter change without entering the containment envelope.
Dental, mental health and inpatient
The dental suite handles aerosol-generating procedures at 8 to 10 ACH with high-volume evacuation at the chair. The mental health observation unit follows the cell-block specification with additional acoustic isolation between observation cells via double-wall acoustic ductwork. The inpatient ward runs at 6 ACH per ASHRAE 170, with private rooms preferred for prolonged stay. The infirmary is bounded by AS 4072.1 Class C construction at the secure perimeter — security door, security wall, Class C sealed duct penetration — and the full document pack is countersigned by both the operator and the state health authority before handover.
Workshop and industries — fume cupboards and industrial exhaust
Correctional facilities run industries — workshops where inmates work for vocational training and for revenue generation. The industries cover joinery, metal fabrication, automotive, textiles, printing, food preparation and laundry. Each industry imposes its own ventilation brief, and the larger workshops include fume cupboards or local exhaust ventilation comparable to a vocational education facility or light industrial workshop.
Fume cupboards and welding fume
Fume cupboards follow AS/NZS 2243.8 for performance and AS 1668.2 for outdoor air supply, with dedicated exhaust, backdraft damper, isolation switch for service and a discharge stack clear of any intake. Duct material is stainless 304 for mild chemistry, stainless 316 for aggressive chemistry and PVC or PP for strong acid, with sealed Class A seam in every case. Metal fabrication workshops generate fume from welding, grinding and cutting — metal oxides, abrasive dust, trace silica — captured at the source under Australian WHS regulations through a moving arm or boom-mounted hood within 300 mm of the work piece, routed to a centralised filtration unit with baghouse and HEPA polish stage before discharge. Capture flow per station is typically 1,000 to 2,000 m³/h, duct sized for 15 to 20 m/s capture velocity and 8 to 10 m/s transport velocity, galvanized or stainless sealed-seam with cleanout access at every junction.
Textiles, printing and joinery
Textile workshops generate lint and chemical exhaust from dyeing, captured at source through a particulate filter. Printing workshops generate VOC exhaust from inks and solvents, captured at the press through a carbon filter. Joinery workshops generate sawdust at substantial volumes, captured at the saw and planer through a cyclone separator with discharge to a baled or bagged waste stream. Each workshop is on its own AHU isolated from the cell block and visitor centre, with industrial-grade sealed-seam ductwork, accessible cleanouts and integration with the workshop fire suppression. The pressure cascade is held negative on the workshop relative to surrounding circulation.
The major Australian correctional projects 2024–2030
Australia is in the middle of the largest correctional infrastructure programme of the past forty years. State and federal capital programmes have committed multi-billion-dollar pipelines covering new builds, expansions and major refurbishments across every state and territory. Each project carries an HVAC ductwork scope covered by the standards stack and the operator manual described above. The list below covers the projects with confirmed scope through 2030 and the operators delivering them.
Western Plains Correctional Centre (Victoria)
Western Plains Correctional Centre at Lara is one of the largest correctional builds in Australian history — a 1,300-bed maximum security men's facility on the existing Barwon Prison site, delivered for Corrections Victoria. The project carries a major HVAC scope across cell accommodation, day rooms, dining, kitchen, laundry, infirmary, programs and visits. Cell-block ductwork is to the Corrections Victoria custodial design standard with the 96 mm contraband threshold, 6 mm steel mesh, sealed-seam construction and tamper-resistant grilles. Kitchen exhaust is sized for the full population three meals per day, with Type 1 grease ductwork in stainless 316 and N+1 redundancy on every fan.
Casuarina Prison expansion (Western Australia)
Casuarina is the WA Department of Justice flagship maximum security men's facility south of Perth. The expansion adds accommodation buildings and upgrades the central kitchen, laundry and infirmary capacity. Specification follows the WA Custodial Infrastructure Design Standard, with cell ACH at the upper end, AS 4072.1 Class C at every perimeter penetration, stainless 304 throughout the laundry exhaust, and additional respiratory isolation cells specified to ASHRAE 170 with HEPA exhaust direct to atmosphere.
Junee Correctional Centre (New South Wales)
Junee is the largest privately operated correctional facility in NSW, operated by GEO Group Australia under contract to NSW Corrective Services. Recent expansion adds accommodation and program space with HVAC scope covering new cell blocks, an expanded kitchen and an upgraded visitor centre. Specification adopts the NSW Corrective Services Capital Works Design Standard plus the GEO Group internal manual, with the visitor centre on a fully isolated AHU and integrated drug detection in the return air path.
Long Bay Hospital expansion (New South Wales)
Long Bay Hospital is the secure healthcare facility within the Long Bay Correctional Complex in Sydney. The expansion adds inpatient capacity, mental health observation, dental and respiratory isolation. The mechanical specification is dual-stack — ASHRAE Standard 170 for healthcare ventilation and AS 4072.1 Class C for the secure perimeter — with respiratory isolation cells at 12 ACH negative, HEPA at exhaust, and full cascade verification at commissioning.
Capricornia and Borallon Correctional Centres (Queensland)
The Capricornia Correctional Centre at Rockhampton (sometimes referred to as Central Queensland Correctional Centre) and Borallon Correctional Centre west of Brisbane are the two flagship Queensland projects. Capricornia is undergoing accommodation expansion and major kitchen and laundry upgrade. Borallon is a maximum security men's facility undergoing infrastructure renewal across mechanical and electrical systems. Both work to the Queensland Department of Justice and Attorney-General design standard, with cell-block contraband rules, stainless 316 kitchen Type 1 ductwork and ASHRAE 170 infirmary integration as standard.
Adelaide Women's Prison and Bandyup Women's Prison
Adelaide Women's Prison at Northfield (SA) and Bandyup Women's Prison at Middle Swan (WA) are the principal women's facilities in their respective states, both undergoing accommodation, programs and infirmary expansion. The mechanical specification reflects the unique women's brief — dedicated mother-and-baby accommodation with healthcare-grade ventilation, programs space supporting trauma-informed care, and an infirmary with antenatal and post-natal capability. Cell-block ductwork follows the standard contraband rules, with day room and program space at the lower end of the ACH band reflecting longer dwell time outside the cell.
Banksia Hill Detention Centre (juvenile)
Banksia Hill Detention Centre at Canning Vale is the principal juvenile detention facility in WA. Specification follows the WA juvenile design standard, which adopts the ACA juvenile reference plus the contraband threshold and mesh specifications used in adult facilities. The juvenile brief shifts more air handling capacity to program and recreation spaces — classroom, gymnasium, library and outdoor program areas each carrying their own AHU and pressure cascade. The infirmary is sized for paediatric and adolescent care with mental health observation as a major component.
Holtze Correctional Centre (Northern Territory)
The Holtze Correctional Centre south of Darwin is the principal facility in the NT. The mechanical brief overlays the standard correctional rules with NT tropical climate constraints — high outdoor air enthalpy, monsoonal humidity peaks and cyclone wind loading on rooftop plant. Duct material is galvanized AS 1397 G2 with corrosion-resistant alternatives in any externally exposed run, sealed-seam construction throughout, and AHU plant designed for high latent load and high wind static pressure.
Operators delivering the pipeline
Five operators deliver the bulk of the Australian correctional pipeline: GEO Group Australia (Junee, Fulham, Parklea), Serco Australia (Acacia, Clarence), NSW Corrective Services (Long Bay, Goulburn, Cessnock, Lithgow, Special Purpose Centre), Corrections Victoria (Barwon, Loddon, Dame Phyllis Frost, Western Plains) and the WA Department of Justice (Casuarina, Hakea, Banksia Hill, Bandyup, Albany, Bunbury). Each operator carries its own facility design manual, and the project mechanical specification is the union of public standards plus the operator manual under NDA.
24/7 redundant operation — N+1 minimum
A correctional facility is occupied every hour of every day. Ventilation that fails at 2 a.m. on a Sunday is a duty-of-care incident within hours. The mechanical specification therefore includes N+1 redundancy on every air handling system serving cells, the kitchen, the infirmary and any holding area, plus standby generator capacity covering the full HVAC load.
N+1 fans, chillers and DX units
N+1 means one more unit than the minimum required to deliver the design load. A 4-fan AHU carries 5 fans, with any one fan out of service without dropping design air flow. The same logic applies to chillers, DX units, pumps and exhaust fans. The N+1 unit is wired and piped with isolation valves and dampers so it can be brought into service without shutting down the AHU, and the BMS rotates the standby through the duty position on a regular schedule so it is not sitting cold for years and failing on first start. For respiratory isolation, kitchen and laundry exhaust the redundancy extends to the discharge path — a single stack carrying the full load is a single point of failure, so the discharge splits across two stacks with backdraft dampers, with the BMS shifting load within 30 seconds on stack failure.
Standby generator and damper fail-safe
Standby generators carry the full HVAC load — cells, kitchen during meal service, laundry during processing and infirmary at all times. The generator is sized for connected mechanical load plus lighting, security and life safety, with auto-transfer switch cut-over within 10 seconds of grid loss. Critical systems — infirmary respiratory isolation exhaust, kitchen fire suppression, security control room — are also on UPS bridging the cut-over interval. Fuel storage is typically 72 hours full-load operation, with refuelling logistics confirmed in the emergency operations plan. Critical exhaust systems run on UPS-backed control circuits so dampers fail to a safe state on power loss — respiratory isolation exhaust damper fails open, kitchen fire damper fails closed, cell-block return damper holds the pressure cascade. The BMS itself runs on redundant servers in the security control room with mirrored backup on a security-rated VLAN isolated from any internet-facing system.
The air gap requirement at perimeter walls
A perimeter wall in a correctional facility is more than a structural and acoustic separator. It is a security envelope. Voice transfer through a duct penetration in a perimeter wall is a communication channel between cells and external areas, and contraband transfer through a duct penetration is a smuggling vector. The mechanical specification therefore requires a physical air gap and acoustic break at every perimeter-wall duct penetration.
The air gap is implemented as a plenum constructed within the wall thickness, with the duct entering the plenum on one side and leaving on the other side, separated by a non-acoustic-bridging spacer. The plenum is large enough that direct line-of-sight between the two duct openings is broken by an internal baffle. Voice transfer is attenuated by the baffle, the air path within the plenum and the absorptive lining on the plenum walls. Contraband transfer is refused by 6 mm steel mesh on every duct opening into the plenum.
The air gap detail is verified at commissioning under AS 4072.1 Class C sign-off. The verification includes acoustic testing across the wall — Sound Transmission Class 50 minimum or equivalent — and physical inspection of every penetration. The corrections operator countersigns the AS 4072.1 Class C completion certificate alongside the structural and fire engineer, and the certificate is part of the building handover pack.
SBKJ machine configuration for correctional ductwork
Correctional ductwork imposes specific demands on the duct production line. The ductwork mill on a correctional project has to produce galvanized and stainless duct in the same shift, sealed-seam Class A construction across both materials, security mesh integration as a routine operation, and the stiffening pattern required to resist tampering. The SBKJ SBAL-V auto duct line is the firm's reference configuration for institutional projects of this scale.
SBAL-V — galvanized and stainless
The SBAL-V is a coil-fed auto duct line producing rectangular duct from coil width 1,250 to 1,550 mm and thickness 0.5 to 1.6 mm. The line accepts galvanized AS 1397 G2, stainless 304 and stainless 316, with tooling adjustment between materials via quick-change rollers. For a correctional project the line produces galvanized for general areas and cell-block supply, stainless 304 for laundry and infirmary isolation exhaust, and stainless 316 for kitchen Type 1 grease duct — all from the same line, with material change-over in less than 30 minutes. The line produces sealed-seam Class A construction as standard, with a Pittsburgh seam reinforced with adhesive sealant and a clinch lock holding the AS/NZS 4254 Class A leak rating across the duct life, and TDF flange or welded butt-strap on the transverse joint.
Security mesh integration and Class A verification
Security mesh is integrated into the duct at fabrication, not as a field retrofit. The SBAL-V is configured with a mesh feed station that accepts 6 mm woven steel and welds or pins the mesh to the duct frame at every grille and register opening before dispatch. The mesh frame is a structural element of the duct, the grille face is fixed to the frame with one-way pins, and the assembly welded into the wall opening with a security perimeter. The single-delivery model accelerates installation, eliminates field welding (a security and safety risk in occupied facilities) and reduces the risk of mesh omission. Class A leak rating is verified at the mill before dispatch — each batch sample-tested at rated pressure, the result recorded in the delivery pack, the as-installed system re-verified by the project commissioning team with the operator witnessing. For correctional projects the Class A verification is part of the security ductwork sign-off, because a leak in a cell-block supply means odour, infectious load and the pressure cascade are not contained.
Commissioning and handover — the document pack
Custodial sign-off requires a full document pack covering every layer of the standards stack. The pack is countersigned by the operator, the head contractor, the mechanical contractor and the relevant state authority before the facility is accepted. Missing documents block the handover, and an incomplete pack on the security ductwork can delay handover by weeks even if every other system is complete.
Security ductwork specification certificate
The certificate confirms every cell-block, intake, infirmary and visitor centre duct run has been built to the security specification — 96 mm threshold, 6 mm mesh, sealed-seam construction, tamper-resistant grilles, AS 4072.1 Class C at the perimeter. Signed by the mechanical contractor and witnessed by the operator, with the operator's internal audit team sign-off.
AS 4072.1 Class C verification
Every perimeter wall duct penetration is verified to AS 4072.1 Class C by witnessed test confirming the acoustic separation across the wall, the physical separation through the air gap, and the sealed construction of the duct on both sides. The test result is recorded in the verification certificate.
ASHRAE 170 commissioning report
The infirmary commissioning report covers every healthcare-zone parameter — ACH, pressure relationship, filtration class, humidity range, isolation room cascade, HEPA exhaust verification, PC-2 cabinet integration. Signed by the mechanical contractor, commissioning agent and state Department of Health, it is the basis for the infirmary entering clinical service.
AS 1668.2 outdoor air calculation
The outdoor air calculation confirms every space type receives the AS 1668.2 minimum, built from as-built duct and as-commissioned AHU rather than design drawings, signed by the mechanical engineer of record, and confirms the operator uplift above the AS 1668.2 floor.
Kitchen, laundry, pressure cascade, redundancy and contraband audit
The kitchen exhaust certificate confirms Type 1 grease ductwork, fire damper installation, fire suppression integration, capture velocity at every hood, exhaust flow at every fan and cleaning access compliance. The laundry exhaust certificate confirms stainless construction, lint trap, exhaust flow and discharge separation. The infirmary pressure cascade record documents differential pressure at every cascade interface with the AHU at design flow and doors closed. The N+1 redundancy demonstration shows the facility maintaining design ventilation with one fan, chiller, DX unit and generator out of service across cell-block, kitchen, laundry and infirmary systems. The contraband audit confirms every grille removed, inspected and refitted under custodial witness; every opening over 96 mm confirmed with 6 mm mesh; every accessible run swept with a borescope; every fastener confirmed tamper-resistant. The audit is run before any inmate is admitted, and the witness sheets are part of the handover pack.
Common procurement mistakes on correctional projects
The patterns SBKJ engineers see across correctional procurement are consistent enough to be treated as a checklist. The biggest cost overruns and the biggest handover delays trace back to the same handful of decisions made early in the project.
Treating the cell block as commercial ductwork
The most common mistake is specifying the cell block as if it were a commercial office. The contractor builds standard galvanized duct with bolted grilles, standard fastener, no mesh and no AS 4072.1 detail. At commissioning the operator's audit team identifies every contraband risk, and the duct has to be reworked under occupied-site conditions — a far more expensive and slower exercise than building it correctly from the start. The fix is to specify the security ductwork rules at tender stage and to procure from a duct mill that integrates mesh and tamper-resistant fasteners as standard.
Underestimating kitchen exhaust scale
Correctional kitchens serve at hospital scale, three meals per day, every day of the year. Specifying a kitchen exhaust as if it were a small institutional kitchen — 2 m³/s riser instead of 6 m³/s — leads to the riser running at the limit, grease drop-out in the duct and a fire risk that the operator's compliance audit catches at commissioning. The fix is to size the exhaust on actual meal volume, design for 4 to 8 m³/s on the main riser, and use stainless 316 throughout.
Specifying the infirmary as a clinic
A correctional infirmary is a hospital, not a clinic. Specifying the infirmary as if it were a primary care clinic — no respiratory isolation cells, no pressure cascade, no HEPA exhaust — leads to a facility that cannot manage tuberculosis or any other airborne infectious disease. The fix is to apply ASHRAE 170 directly to the infirmary, design for respiratory isolation at 12 ACH negative with HEPA exhaust, and integrate the PC-2 procedure room from day one.
Skipping N+1 redundancy
A single fan on a cell-block AHU is a duty-of-care incident waiting to happen. Skipping the N+1 redundancy to save capital cost is a false economy — the operating cost of fan failures, emergency call-outs and risk of an incident exceeds the saved capital cost within the first decade of operation. The fix is to specify N+1 fan, N+1 chiller, N+1 DX unit and N+1 generator on every system at tender stage.
Single-source duct mill without security ductwork track record
Procuring duct from a mill that does not have a track record on correctional projects leads to misunderstandings on the security ductwork rules. The mill builds the duct correctly to commercial standard, but does not understand the 96 mm threshold, the mesh specification or the tamper-resistant fastener requirement. The fix is to procure from a mill with documented correctional, defence or healthcare experience and to specify the security ductwork rules in the duct purchase order, not just in the project specification.
How SBKJ works on correctional projects
SBKJ Group has supplied auto duct line, spiral tubeformer and TDF flange machinery used in correctional, defence, healthcare and institutional projects across 100+ countries. The firm operates from Box Hill North, Victoria, with engineering, sales and after-sales staff supporting the Australian and Asia-Pacific market. Where a project mechanical contractor builds duct in-house, SBKJ supplies the line. Where the contractor procures duct from a mill, SBKJ engineers walk through the security ductwork specification with the mill team to confirm the 96 mm threshold, the mesh integration, the sealed-seam construction and the AS 4072.1 Class C detail are all in scope.
The firm's reference machine for correctional projects is the SBAL-V auto duct line — galvanized plus stainless option, sealed-seam Class A construction, security mesh integration, full PLC and HMI on Siemens or Mitsubishi, ISO 9001 certified, CE marked, Factory Acceptance Test mandatory before shipment. The line produces duct sized correctly for cell-block, kitchen, laundry and infirmary in a single mill, with material change-over in under 30 minutes between galvanized and stainless. The line is supported by SBKJ engineers on site for installation, mechanical commissioning, electrical commissioning and operator training, with an Australian English-speaking after-sales contact on call from Box Hill North.
Project teams working on the major Australian correctional pipeline — Western Plains, Casuarina, Junee, Long Bay, Capricornia, Borallon, Adelaide Women's, Banksia Hill, Bandyup, Holtze and the operator-led capital programmes — can engage SBKJ for the duct mill specification, the security ductwork integration and the on-site commissioning. The firm carries documented experience on institutional projects of this scale and works to the operator NDA wherever the operator manual is in scope.
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FAQ
What makes correctional ductwork different from commercial ductwork?
Correctional ductwork has four engineering constraints commercial ductwork does not — anti-contraband construction with no internal voids and no openings larger than 96 mm without security mesh, tamper-resistant grilles and registers using one-way fasteners or welded frames, AS 4072.1 Class C sealed-seam construction at perimeter wall penetrations, and N+1 redundancy on every air handling system because the building is occupied 24/7.
What air change rates apply to cell blocks?
Australian correctional cells are designed at 6 to 12 ACH depending on cell type and operator. Maximum security and segregation cells run at the upper end with negative pressure relative to the corridor; protective custody and dormitory units run at the lower end. AS 1668.2 sets the floor on outdoor air; operators usually uplift to 12 to 15 L/s per occupant.
What standards govern infirmary ventilation in a prison?
Prison infirmaries follow ASHRAE Standard 170 for ventilation of healthcare facilities, AS 1668.2 for outdoor air rates and the relevant state Department of Health guidelines. Respiratory isolation cells require 12 ACH negative pressure, sealed envelope, HEPA exhaust to atmosphere with anteroom. PC-2 procedure rooms follow AS/NZS 2243.3 for laboratory containment.
How is anti-contraband design verified during commissioning?
Verification is by physical inspection — every grille removed and refitted under custodial witness, every duct opening larger than 96 mm confirmed with 6 mm woven steel mesh, every accessible run swept with a borescope to confirm no concealment voids, every penetration through a perimeter wall verified for AS 4072.1 Class C separation. The operator countersigns the security ductwork sign-off before any cell block is handed over.
What HVAC ductwork is needed for kitchen and laundry at scale?
A 1,500-bed facility serves around 4,500 meals per day. Exhaust hoods discharge through Type 1 grease ductwork at 120 °C continuous rating, with flow rates from 4 to 8 m³/s per cooking line. Laundry exhaust handles high humidity, lint and antimicrobial chemistry — galvanized or stainless 304 with sealed seams, lint trap upstream of the fan, and discharge clear of any intake by 6 m to AS 1668.2.
What duct material is specified for Australian correctional projects?
Galvanized AS 1397 G2 is the default for general areas and cells. Stainless 304 is specified at laundry and infirmary respiratory isolation exhaust. Stainless 316 is specified at kitchen Type 1 grease duct. The SBKJ SBAL-V auto duct line accepts both galvanized and stainless coil and produces sealed-seam Class A ductwork with security mesh integration as standard.
Which Australian correctional projects are in pipeline 2024 to 2030?
Western Plains (VIC), Casuarina expansion (WA), Junee (NSW), Long Bay Hospital expansion (NSW), Capricornia and Borallon (QLD), Adelaide Women's expansion (SA), Banksia Hill (WA juvenile), Bandyup Women's (WA) and Holtze (NT). Operators include GEO Group Australia, Serco Australia, NSW Corrective Services, Corrections Victoria and the WA Department of Justice.
What redundancy is required for correctional HVAC?
N+1 minimum on every air handling system serving cells, the kitchen, the infirmary and any holding area. Standby generators carry the full HVAC load with auto-transfer cut-over within 10 seconds. Critical exhaust systems run on uninterruptible power so dampers fail to a safe state on power loss.
