Industrial Bakery HVAC Duct Guide — Bread, Pastry, Cake, Cookie, Biscuit, Tortilla and Pie Manufacturing

Why industrial bakery HVAC is its own engineering category

Industrial bakery and biscuit manufacturing is the only food-manufacturing sector in Australia where the single most consequential HVAC duct hazard is not corrosion, contamination or refrigerant exposure — it is dust deflagration. A modern integrated Australian bread, biscuit, pastry or pie plant runs perhaps fifteen distinct climatic envelopes inside one building footprint, but the engineering brief is dominated by the recognition that wheat flour, sugar and cocoa are all classified as combustible dust under AS 3957 and NFPA 660 (the 2025 consolidated combustible dust standard), and the silo headspace, the conveying ductwork, the sifter discharge, the mixer hopper extract and the dust collector primary cyclone are all hazardous areas under AS/NZS 60079.10.2 dust atmospheres — Zone 21 or Zone 22 classification across the dust handling envelope. The 2025 NFPA 660 standard consolidates the previous NFPA 61 agricultural dust, NFPA 484 metal dust, NFPA 654 combustible particulate solids and NFPA 664 wood dust into a single consolidated reference that covers wheat, rye, oat, corn and rice flour, sugar, cocoa, starch and bakery enzyme dust in a single technical envelope, and the standard is rapidly becoming the reference of choice for Australian bakery engineering specifications.

Beyond the dust deflagration hazard the bakery HVAC envelope also has to manage the 220 to 260 degree Celsius continuous tunnel oven exhaust under NFPA 86 (Standard for Ovens and Furnaces), the 80 to 85 percent relative humidity proofing room atmosphere, the carbon dioxide load from yeast fermentation, the LPG or natural gas combustion products from the oven burner train, the bread cooler tunnel and rapid cooling envelope, the cooked-product cooling cross-contamination risk under FSANZ 3.2.2 and HACCP, the retarder and freezer at minus 20 to minus 40 degrees Celsius on the pie pastry and IQF product lines, the ammonia refrigeration plant under AS/NZS 1677 and AS/NZS 5149, and the oil mist deep-fry exhaust on donut, churro and pie pastry operations under NFPA 96. Every Australian export-licensed bakery — Arnott's exporting Tim Tam to the United States, Canada, the United Kingdom and ASEAN under AQIS export licence, Mondelez Cadbury exporting biscuit, Sara Lee Australia exporting dessert and pie product — runs the full multi-standard envelope.

SBKJ Group has supplied auto duct production lines, spiral tubeformers, stitchwelders, plasma cutters and longitudinal seam welders into the Australian industrial bakery and biscuit sector for more than a decade. Our engineers from the Box Hill North VIC office have walked the Goodman Fielder Erskine Park NSW Wonder White line, the Arnott's Huntingwood NSW biscuit floor (the largest biscuit operation in Australia), the Four'N Twenty Bairnsdale VIC pastry production envelope, the Patties Foods meat pie line, the Mrs Mac's West Perth automation rollout, the Allied Pinnacle Picton NSW flour mill expansion and the Manildra Group Manildra NSW wheat starch and gluten plant. We have seen what fails, what stands up to a fifteen-year flour-dust environment, and what the AQIS auditor and the WorkSafe Victoria inspector flag first when an export-licensed bakery is at risk of suspension or when a flour mill has had a near-miss deflagration event. This guide is written against that field experience. Pricing is held back here because pricing is meaningful only in the context of a specific plant brief; talk to an SBKJ engineer for an itemised landed-cost worksheet that ties scope to scope.

The Australian industrial bakery sector — operators, plants and product categories

Before specifying HVAC ductwork for any bakery the engineering team has to know the product category, the operator, the plant scale, the export licence portfolio and the regulatory envelope. Australia operates one of the most concentrated industrial bakery sectors in the OECD, with two large bread manufacturers controlling more than seventy percent of the sliced bread retail volume, a small number of large biscuit and confectionery manufacturers controlling the long-shelf-life sweet biscuit category, and a fragmented but high-volume meat pie and pastry sector.

Industrial bread — Goodman Fielder, Tip Top and the Wonder Australian Premier Wholesalers footprint

Goodman Fielder is the largest bread manufacturer in Australia and operates the Wonder White, Helga's, Mighty Soft, Wonder Bakery Fresh and Tip Top brands under a single corporate umbrella following the consolidation of the Australian Premier Wholesalers business. Goodman Fielder operates major bread plants at Erskine Park NSW (the largest sliced-bread plant in Australia), Botany NSW, Murarrie QLD, Maroochydore QLD, Burleigh QLD, Beresfield NSW, Smithfield NSW, Brisbane QLD, Wodonga VIC, Wantirna VIC, Brunswick VIC, Adelaide SA and Perth WA. Each plant runs continuous tunnel oven banks of 60 to 90 metre tunnel length, automated mixer and proofing lines, and high-speed slicing and bagging operations. The combined Goodman Fielder bread production is several hundred thousand loaves per day across the national footprint.

Tip Top Bakeries — now part of the Goodman Fielder group — operates plants at Erskine Park NSW (the Tip Top facility runs adjacent to the Wonder Bakery operation in the same Erskine Park precinct), Wodonga VIC and Pinjarra Hills QLD. Tip Top is the largest dedicated bakery brand by retail recognition and runs both sliced bread and bread roll product across the national distribution network.

The Goodman Fielder Erskine Park NSW Wonder White line represents the most engineered industrial bread plant in Australia. The continuous tunnel oven runs at 220 to 230 degrees Celsius baking chamber temperature with a 60 to 90 metre tunnel length and a throughput of several thousand loaves per hour. The flour silo and conveying system handles in excess of 150 tonnes per day of flour from Allied Pinnacle, Manildra Group, GrainCorp and other miller suppliers. Yeast supply is from Mauri ANZ or Lallemand Yeast. The full HVAC envelope — flour dust extraction, mixer extract, proofing chamber dewpoint control, oven exhaust, bread cooler tunnel ventilation, slicing and bagging dust extraction, and dispatch chilling — sits at the top end of Australian industrial bakery complexity.

Bakery franchise chains — Bakers Delight, Brumby's, Lawson's, Crust Pizza

Australia operates the most successful retail bakery franchise sector in the OECD. Bakers Delight operates more than 700 stores nationally with a central commissary model where prepared dough is shipped from regional production centres to the in-store ovens for final baking. Brumby's Bakery (owned by Withers Group) operates more than 300 stores nationally on a similar franchise model. Lawson's Bakery and other regional franchise chains operate smaller but locally significant footprints. Crust Pizza operates the largest dedicated pizza franchise chain in Australia with a substantial commissary dough operation feeding the wood-fired deck oven model at the store level.

The HVAC duct scope for a bakery franchise chain divides between the regional commissary operations (which are scaled-down industrial bakery plants with mixer, proofing, partial baking and chilled distribution) and the in-store retail bakery operations (which run NCC Class 6 retail bakery shop HVAC under AS 1668.2 with NFPA 86 compliance on the in-store deck or rotating ovens). The commissary HVAC envelope is materially the same as a small Goodman Fielder regional bread plant.

Biscuit and confectionery — Arnott's, Mondelez Cadbury and the long-shelf-life sweet sector

Arnott's (owned by KKR following the Campbell Soup Company divestiture, with the brand history tracing back to the William Arnott biscuit operation) is the largest biscuit manufacturer in Australia and operates the most recognisable biscuit brand portfolio in the Australian retail food sector. Arnott's runs major plants at North Strathfield NSW (the original headquarters and oldest operating plant), Huntingwood NSW (the largest biscuit plant in Australia and the principal Tim Tam production site), and Marleston SA. The product portfolio covers Tim Tam, Shapes, SAO, Jatz, Vita-Weat, Salada, Iced VoVo, Mint Slice and dozens more under the broader Arnott's umbrella. Arnott's is also the largest Australian biscuit exporter, with substantial volume into the United States, Canada, the United Kingdom and ASEAN markets under AQIS export licence.

The Arnott's Huntingwood NSW biscuit oven is the longest continuous biscuit tunnel oven in Australia at over 100 metres tunnel length and represents the most complex single-line bakery oven exhaust ducting installation in the country. NFPA 86 governs the oven exhaust scope — high-temperature 316L stainless construction, fully welded longitudinal seams, dedicated combustion air supply, flue gas extract sized for the burner heat release, and explosion relief on the combustion chamber and gas train. The flour, sugar and cocoa handling envelope upstream of the oven is the most demanding dust extraction scope in any Australian biscuit operation.

Mondelez International operates the Cadbury chocolate biscuit and confectionery portfolio in Australia under the Cadbury, Mint Slice and Royal Dansk brands. The Mondelez Hobart Cadbury plant is one of the largest chocolate manufacturing operations in the southern hemisphere and combines the chocolate confectionery line, the chocolate-enrobed biscuit line and the cocoa powder handling envelope into a single integrated facility. Cocoa dust deflagration risk is the single most significant Zone 21 hazardous area concern at the Mondelez operation, alongside sugar dust handling in the confectionery line.

Meat pie and pastry — Four'N Twenty, Patties Foods, Mrs Mac's, Patrick's, Sara Lee

Australian meat pie and pastry is a globally distinctive sector — Australia consumes more meat pies per capita than any other OECD country and the sector supports several large-scale dedicated manufacturers. Four'N Twenty (owned by Patties Foods) at Bairnsdale VIC is the largest Australian meat pie manufacturer and operates the most automated pie line in the country. The Four'N Twenty product portfolio covers traditional meat pie, party pie, sausage roll, pasty and frozen pastry product, distributed through every major Australian supermarket chain, every major sporting venue food service operator and the export market into New Zealand and the United Kingdom.

Patties Foods at Bairnsdale VIC operates as the integrated manufacturing platform for Four'N Twenty and related Patties brands. The Bairnsdale facility runs substantial freezing and IQF capacity for both the pie pastry pre-freeze (minus 25 to minus 35 degrees Celsius) and the IQF finished cooked pie product (minus 30 to minus 40 degrees Celsius). Ammonia refrigeration plant under AS/NZS 1677 supports the cold chain envelope.

Mrs Mac's at West Perth WA is the largest dedicated meat pie manufacturer in Western Australia and the second-largest Australian meat pie brand by retail recognition. Mrs Mac's runs meat pie, sausage roll and pasty production on highly automated lines with substantial chilled and frozen distribution capacity.

Sara Lee Australia — now part of the broader Sara Lee Frozen Bakery business under various ownership changes — runs the largest dessert and frozen bakery brand in Australia. Product covers frozen cake, frozen pie, danish pastry and dessert product across both retail and food-service distribution.

Patrick's Pies covers the Cooke's Pies and Sargent's Pies brand portfolio in the Sara Lee Australia stable, with substantial pie and pastry product across the Australian retail and food-service market.

Allied bakery operators — Beerenberg, Mondelez, Continental, Bega, Schweppes, McCormick

Australia hosts a number of specialist allied bakery and food-manufacturing operators that overlap with the bakery HVAC engineering scope. Beerenberg at Hahndorf SA operates the largest Australian jam and condiment producer with a substantial breakfast product portfolio. Continental (Unilever Australia) operates the largest Australian dry soup, sauce mix and prepared food mix manufacturer. Bega Cheese (ASX:BGA) operates the Tatura VIC dairy operation and the Vegemite production (acquired from Mondelez in 2017). Suntory Beverage & Food operates the Schweppes Australia beverage business with substantial mixer drink and adult soft drink portfolio. McCormick Foods Australia at Geelong VIC operates the largest Australian spice and seasoning manufacturer.

Flour milling and bakery ingredient — Allied Pinnacle, Manildra, GrainCorp, Mauri, Lallemand

Upstream of the bakery and biscuit manufacturers sits the flour milling and bakery ingredient supply tier. Allied Pinnacle at Picton NSW operates the largest Australian flour milling operation, supplying flour to Goodman Fielder, Tip Top, Arnott's and the broader Australian bakery sector, plus the JOY-cell yeast brand. Manildra Group at Manildra NSW operates Australia's largest flour mill plus a substantial wheat starch and gluten production operation — the gluten and wheat starch dust handling envelope at Manildra is one of the most demanding Zone 21 hazardous area duct scopes in Australian food manufacturing. GrainCorp (ASX:GNC) operates the largest Australian grain and oilseed handler with substantial flour milling and edible oils operations. Mauri ANZ and Lallemand Yeast Australia operate the two principal Australian baker's yeast suppliers, with airborne fungi cross-contamination concerns adding a further hygiene dimension to the bakery HVAC engineering scope.

What makes industrial bakery HVAC mechanically distinctive

Flour dust deflagration — the single biggest hazard

Wheat flour carries a dust deflagration index (Kst) in the 100 to 160 bar metre per second range across the common Australian milling grades. Rye flour, oat flour, corn flour, rice flour and the gluten and wheat starch products from Manildra all fall in the same range. AS 3957 (Industrial dust hazard standard) and NFPA 660 (Standard for Combustible Dusts and Particulate Solids, the 2025 consolidation) both classify flour at this Kst range as St1 explosible dust at the lower end and low-end St2 at the upper end. The minimum explosible concentration is 50 to 60 grams per cubic metre of airborne dust, and the minimum ignition energy is well under 100 millijoules — well below the energy of a routine static discharge from a worker's clothing.

The practical implication is that any space where airborne flour dust can accumulate at or above the minimum explosible concentration is a hazardous area under AS/NZS 60079.10.2 (Classification of areas — combustible dust atmospheres). The silo headspace, the bulk conveying ductwork, the sifter discharge, the mixer hopper extract and the dust collector primary cyclone all fall into Zone 21 (dust cloud likely to occur in normal operation) or Zone 22 (dust cloud unlikely but possible) classification. The 1997 Westwego Louisiana sugar dust deflagration (14 fatalities), the 2008 Imperial Sugar Port Wentworth Georgia explosion (14 fatalities, 36 injuries), and successive flour, sugar and metal dust incidents catalogued by the United States Chemical Safety Board reinforce the consistent pattern: a single ignition source in a Zone 21 area triggers a primary deflagration, which lifts settled dust from surrounding structure into airborne suspension, which feeds a secondary deflagration that destroys the plant. The HVAC duct response is the combined NFPA 68 deflagration venting (vent the design overpressure to safe outdoor location), NFPA 69 explosion isolation (prevent flame and pressure propagation between connected vessels), full bonding and grounding (prevent static spark accumulation), conductive duct construction with verified earth continuity, elimination of internal duct insulation and horizontal dust traps, and routine clean-down to maintain settled-dust load below the secondary deflagration threshold.

Baker's asthma and occupational respiratory exposure

Beyond the deflagration hazard, flour dust carries a substantial occupational respiratory exposure hazard. Safe Work Australia sets the wheat flour workplace exposure standard at 10 milligrams per cubic metre 8-hour time-weighted average inhalable fraction, and 5 milligrams per cubic metre respirable fraction. Bakery enzyme aerosol (alpha-amylase, xylanase, glucose oxidase) is the principal sensitiser in occupational baker's asthma and the second-most-common cause of occupational asthma claims in Australia after isocyanate-induced asthma. Continuous exposure even at the workplace exposure standard accumulates sensitisation risk across a worker's career — with onset typically 5 to 15 years into a baking career.

The HVAC duct response is local exhaust ventilation at every flour dust generation point at 0.5 metres per second minimum capture velocity per the ACGIH Industrial Ventilation Manual, dedicated dust collector ductwork separate from the building general exhaust to prevent dust recirculation, and clean dilution supply air at 25 to 30 air changes per hour over the bench-work and mixer zones. Goodman Fielder Erskine Park, Tip Top Wodonga, Bakers Delight central commissary and Arnott's Huntingwood all run engineered local exhaust ventilation as standard.

Sugar dust and cocoa dust — the confectionery extension

Sugar dust carries a Kst in the 130 to 160 bar metre per second range, also St1 explosible dust under AS 3957 and NFPA 660. Cocoa dust runs Kst 100 to 130 in the same range. Both are minimum-explosible at 60 to 70 grams per cubic metre airborne concentration. The Australian biscuit and confectionery sector — Arnott's Huntingwood biscuit production, Arnott's North Strathfield, Arnott's Marleston, Mondelez Cadbury operations covering Tim Tam, Mint Slice and Royal Dansk Danish butter cookie equivalents, plus the broader confectionery sector running chocolate enrobing lines — handles cocoa powder, sugar and chocolate crumb at industrial scale. The same Zone 21 hazardous area classification applies to sugar and cocoa handling that applies to flour, and the same NFPA 68 deflagration venting, NFPA 69 isolation, bonding and grounding, conductive duct construction and clean-down requirements apply. The chocolate enrobing line additionally generates airborne cocoa dust on the enrober extract duct, requiring continuous extract and dedicated dust collector with full hazardous area compliance.

Continuous tunnel oven exhaust at 220 to 260 degrees Celsius

The continuous tunnel oven is the single largest HVAC fixture in any industrial bread or biscuit plant. Baking chamber temperatures run 220 to 230 degrees Celsius for white sandwich loaf, 230 to 245 degrees Celsius for sourdough, 245 to 260 degrees Celsius for fruit loaf and rye. Biscuit ovens run 200 to 260 degrees Celsius depending on the product (Tim Tam shells, Shapes, savoury cracker variants). The exhaust stack ductwork at the canopy hood outlet runs at 180 to 220 degrees Celsius once mixed with capture room air, dropping to 80 to 120 degrees Celsius further downstream after dilution and any heat recovery economiser. NFPA 86 (Standard for Ovens and Furnaces) governs the oven exhaust scope — high-temperature 316L stainless construction, fully welded longitudinal seams, dedicated combustion air supply, flue gas extract sized for the burner heat release, and explosion relief on the combustion chamber and gas train. Heat recovery economiser ductwork pre-heats the bakery hot water supply and reduces the natural gas or LPG demand by 15 to 25 percent on the next baking cycle.

Rack oven, rotating oven and deck oven banks

Outside the continuous tunnel oven envelope, Australian bakeries run rack ovens (small-batch artisan and franchise commissary), rotating ovens (artisan sourdough and specialty product) and deck ovens (pizza, pastry, traditional bread roll). Each oven type has its own exhaust capture requirement under NFPA 86. Bakers Delight, Brumby's and the smaller franchise commissary operations run rack and deck oven banks at scale. Crust Pizza operates the largest Australian wood-fired and gas-fired deck oven population through its franchise network, with creosote and VOC emission as a distinctive operating challenge on the wood-fired variant. Wood-fired deck oven exhaust is 316L stainless throughout with NFPA 96 grease-laden exhaust treatment because the wood combustion products and the pizza topping (cheese, sauce, meat) all contribute to a grease-laden discharge.

Proofing room humidity control at 30 to 40 degrees and 80 to 85 percent RH

Bread proofing — the controlled fermentation of yeast-leavened dough before baking — runs at 30 to 40 degrees Celsius with 80 to 85 percent relative humidity to support optimal yeast metabolism and to prevent skin formation on the dough surface. Industrial bread plants operate continuous proofing chambers integrated directly into the production line, with the dough entering at ambient and progressing through the proofing tunnel for 45 to 90 minutes before discharge to the oven in-feed. The HVAC engineering response is dewpoint-conditioned supply air rather than room reheat: the supply air handler chills outdoor air to the target dewpoint, then reheats and humidifies to the proofing temperature and humidity set point. Duct construction is 316L stainless throughout because the proofing room atmosphere is acid-aerosol-rich (sourdough plants generate lactic and acetic acid vapour from the levain culture) and the warm-humid envelope drives aggressive corrosion of any galvanised duct above the chamber.

Air velocity at the dough surface is 0.3 to 0.5 metres per second to avoid skin formation. CO2 from yeast fermentation is exhausted continuously and the room runs at neutral or slightly negative pressure relative to the dry mixer floor. Yeast fermentation generates approximately 1.5 to 2.5 grams of CO2 per kilogram of dough across the proofing cycle, and a Goodman Fielder Erskine Park scale operation can release several hundred kilograms of CO2 per shift through the proofing room exhaust. CO2 monitoring with alarm at 5000 ppm 8-hour TWA is the standard installed configuration.

Bread cooler tunnel and rapid cooling

Downstream of the oven sits the bread cooler tunnel — a 60 to 90 metre tunnel where the freshly baked loaf cools from 95 to 100 degrees Celsius core temperature to 30 to 35 degrees Celsius surface temperature before slicing. The cooler tunnel ventilation handles substantial steam release from the cooling loaf (typically 4 to 6 percent moisture release across the cooling cycle), aerosolised yeast and bakery enzyme, and the residual warm-humid envelope from the oven exhaust capture. Duct construction is 316L stainless throughout with welded longitudinal seams to manage the warm-humid corrosion envelope.

Slicing, bagging and packaging

The high-speed bread slicer is the most distinctive ergonomic and dust-generation point on a continuous bread line. Each slice generates a small flour and crumb dust release, and a Goodman Fielder Erskine Park scale slicer running thousands of loaves per hour generates substantial airborne crumb dust requiring dedicated local exhaust at 0.5 metres per second minimum capture velocity. The bagging line generates polyolefin film dust and heat seal smoke, requiring separate exhaust capture for the heat seal jaws.

Cooked product cooling cross-contamination

The single highest cross-contamination risk in an industrial bakery is the airborne transfer of pre-bake microbial load (raw dough yeast, bakery enzyme, lactic acid bacteria from sourdough levain) to the post-bake product zone during cooling. FSANZ 3.2.2 and HACCP require positive separation between pre-bake and post-bake hygiene zones. The HVAC pressurisation cascade runs the post-bake cooler, slicer and bagger at plus 15 to plus 25 Pascals relative to the mixer, proofer and oven in-feed at minus 5 to minus 10 Pascals. Sealed-seam AS 4254 Class B or SMACNA Class A duct construction maintains the cascade.

Pie pastry and IQF freezer envelope

Australian meat pie and pastry manufacturers run substantial freezing capacity on both the raw pie pastry pre-freeze (to allow downstream handling without dough deformation) and the IQF finished cooked product hold. Pie pastry pre-freeze runs minus 25 to minus 35 degrees Celsius. IQF on the finished cooked pie runs minus 30 to minus 40 degrees Celsius. R-717 ammonia or R-744 CO2 refrigeration plant under AS/NZS 1677 supports the cold chain. The ammonia compressor room is a Zone 2 hazardous area under AS/NZS 60079 with emergency ventilation at 30 air changes per hour, wet scrubber discharge, continuous ammonia detection with alarm at 15 ppm and shutdown at 25 ppm, and AS 4775 emergency eyewash and shower at every machinery room exit.

Deep-fry oil mist on donut, churro and pie pastry

Donut, churro and certain pastry product lines (filo cup, savoury pastry, pie pastry) operate deep-fry stages at 175 to 195 degrees Celsius. The exhaust hood over the fryer captures oil mist, water vapour and combustion products under NFPA 96 commercial kitchen ventilation requirements. 316L stainless welded-seam grease-tight duct, integrated wet chemical or water mist suppression per AS 1851, 30 degree minimum slope on horizontal runs to drain oil condensate, removable cleaning panels at 3 metre intervals and discharge stack 3 metres minimum clear of any outdoor air intake are the standard requirements.

The bulk flour silo and bulk handling envelope — the start of the HVAC scope

The bulk flour silo and bulk handling envelope is the first HVAC zone in any industrial bakery and is invariably the highest-risk Zone 21 hazardous area under AS/NZS 60079.10.2. A Goodman Fielder Erskine Park scale operation receives bulk flour by tanker truck at 25 to 35 tonnes per delivery, multiple deliveries per day, into a silo bank with combined silo capacity of 500 to 1500 tonnes. The pneumatic conveying from tanker to silo generates substantial airborne dust load and the silo headspace is continuously dust-laden during the discharge cycle.

The HVAC duct engineering brief on the silo bank is dust collector ductwork sized for the peak conveying load, deflagration vent panels on the silo crown sized per NFPA 68 to vent the design overpressure to safe outdoor location, NFPA 69 explosion isolation between the silo and any downstream conveying or mixer hopper, full bonding and grounding of the silo, ducting and conveying piping to a common earth grid, continuous spark detection on the conveying line with quench actuation, and routine internal clean-down of the silo and downstream ductwork to maintain settled dust load below the secondary deflagration threshold. The dust collector itself is a Zone 21 vessel with full deflagration vent panel, explosion isolation valves on both inlet and outlet, and conductive duct construction throughout.

SBKJ supplies the post-collector clean side ductwork in 316L stainless via the SBAL-V auto duct line for rectangular sections and the SBFB-1500 spiral fitting forming line for round conveying duct. The conveying ductwork upstream of the explosion isolation valve is rated to withstand the design deflagration pressure (typically 1.0 to 1.5 barg) with 1.2 to 1.5 millimetre gauge minimum and continuous TIG-welded longitudinal seams from the SB-ZF1500 stitchwelder.

The mixer floor and dough preparation envelope

Downstream of the silo and conveying sits the mixer floor — high-speed continuous mixer banks, dough divider, dough rounder and intermediate proofer. The mixer extract handles the bulk flour dust load liberated during dough mixing, the bakery enzyme aerosol, and the residual moisture release as the dough develops. Mixer floor ambient temperature is 20 to 25 degrees Celsius with controlled humidity at 50 to 60 percent RH to support consistent dough handling. The HVAC supply is dedicated outside air at 15 to 20 air changes per hour, dewpoint-conditioned to the target humidity. Duct construction is 316L stainless on the mixer extract because the warm-humid dough environment generates aggressive corrosion in any galvanised duct above the mixer.

The mixer hopper extract is local capture at 0.5 to 1.0 metres per second capture velocity over the dough discharge point and the flour addition point. The extract routes to the dedicated flour dust collector via NFPA 69 explosion isolation valves. The mixer floor environment is the principal occupational respiratory exposure zone in the plant — bench bakers and mixer operators work in continuous contact with flour dust and bakery enzyme aerosol across the production cycle. Engineered local exhaust ventilation is the principal engineering control for baker's asthma prevention.

Continuous proofing tunnel — the controlled fermentation envelope

The continuous proofing tunnel runs at 30 to 40 degrees Celsius and 80 to 85 percent relative humidity for the 45 to 90 minute proofing cycle. The HVAC duct construction is the most demanding warm-humid envelope in the bakery plant. 316L stainless throughout with continuous TIG-welded longitudinal seams from the SB-ZF1500 stitchwelder. External insulation only because internal insulation accumulates condensate and yeast aerosol. 30 degree minimum slope on horizontal runs to drain condensate. Removable cleaning panels at 3 metre intervals for routine sanitation access.

Air velocity at the dough surface is 0.3 to 0.5 metres per second to balance the dewpoint exchange (necessary to maintain the dough surface at the proofing humidity) with skin-formation avoidance (excess velocity desiccates the dough surface). Supply air is dewpoint-conditioned: the supply air handler chills outdoor air to the target dewpoint, then reheats to the proofing temperature without subsequent humidification. The room humidity tracks the supply air dewpoint directly, which is the most stable humidity-control strategy in continuous bakery production.

CO2 from yeast fermentation is exhausted continuously. A Goodman Fielder Erskine Park scale operation produces several hundred kilograms of CO2 per shift through the proofing room exhaust. Continuous CO2 monitoring with alarm at 5000 ppm 8-hour TWA and shutdown at 30000 ppm STEL is the standard installed configuration. The proofing room runs at neutral or slightly negative pressure relative to the dry mixer floor and the oven in-feed.

Continuous tunnel oven exhaust — NFPA 86 dedicated scope

The continuous tunnel oven exhaust is the most engineered HVAC duct package on a major industrial bread or biscuit plant. The tunnel oven runs 60 to 90 metres tunnel length on a bread line, up to 100 metres on the Arnott's Huntingwood biscuit tunnel. Baking chamber temperature is 220 to 260 degrees Celsius depending on the product line. The exhaust capture canopies sit above the oven loading and unloading ends, with intermediate combustion air supply and intermediate flue gas extracts spaced along the tunnel.

Exhaust capture canopy and stack

The exhaust capture canopy at the oven loading and unloading ends captures the residual oven gas and the immediate steam release from the freshly baked product. The capture canopy runs at 0.5 to 1.0 metres per second capture velocity across the canopy face. Stack ductwork at the canopy outlet runs at 180 to 220 degrees Celsius once mixed with capture room air. The hot section is 316L austenitic stainless steel uninsulated to prevent insulation degradation under the temperature, with fully welded longitudinal seams from the SBKJ SB-ZF1500 stitchwelder. The stack incorporates a heat recovery economiser to pre-heat the bakery hot water supply — recovered heat reduces gas demand by 15 to 25 percent on the baking cycle.

Combustion air supply and flue gas extract

NFPA 86 (Standard for Ovens and Furnaces) requires dedicated combustion air supply interlocked with oven burner operation. Combustion air supply ductwork is dedicated 316L stainless with capacity for 110 to 120 percent of the maximum burner heat release. Flue gas extract is sized for the burner combustion products plus any process moisture release, with explosion relief on the combustion chamber and gas train per NFPA 86 Annex B. The combustion air supply and flue gas extract are mechanically interlocked with the burner control to prevent burner operation under loss of air supply or under exhaust fan failure.

Gas train and burner explosion relief

NFPA 86 Annex B prescribes explosion relief on the natural gas or LPG burner gas train. Vent area is sized to limit the residual pressure (Pred) below the duct and combustion chamber pressure rating in the event of unburnt fuel accumulation and subsequent ignition. The gas train explosion relief discharges to safe outdoor location with no obstruction and no occupied space within the discharge cone.

Heat recovery economiser

The heat recovery economiser at the oven stack pre-heats the bakery hot water supply circuit. Recovered heat reduces natural gas or LPG demand by 15 to 25 percent on the next baking cycle. Economiser construction is 316L stainless plate-finned coil with fully welded coil headers and dedicated drain for condensate recovery. The economiser discharge ductwork at 80 to 120 degrees Celsius is 316L stainless with external insulation.

Bread cooler tunnel and rapid cooling

Downstream of the tunnel oven sits the bread cooler tunnel — a 60 to 90 metre tunnel where the freshly baked loaf cools from 95 to 100 degrees Celsius core temperature to 30 to 35 degrees Celsius surface temperature before slicing. The cooler tunnel ventilation handles substantial steam release from the cooling loaf (typically 4 to 6 percent moisture release across the cooling cycle), aerosolised yeast and bakery enzyme, and the residual warm-humid envelope from the oven exhaust capture.

Duct construction is 316L stainless throughout with welded longitudinal seams to manage the warm-humid corrosion envelope. Air velocity across the cooling loaf is 0.5 to 1.5 metres per second — lower velocity and the cooling rate is insufficient to meet the line speed, higher velocity and surface dehydration produces unacceptable shrinkage. Pressurisation is plus 5 to plus 15 Pascals relative to the oven exhaust capture room to maintain the FSANZ 3.2.2 hygiene zone separation between the pre-bake and post-bake envelopes. Air exchange rate is 20 to 30 air changes per hour with dedicated exhaust to handle the moisture and aerosol load.

The bread cooler tunnel is the principal Listeria audit risk in an industrial bread plant. Standing condensate in the tunnel construction creates the conditions for Listeria proliferation. Duct construction must be vapour-tight at every seam, sloped on horizontal runs to drain condensate to dedicated drains, and free of internal insulation that would accumulate biological load. The Listeria audit findings in Australian bakery plants over the last decade have repeatedly traced back to inaccessible cooler tunnel duct interiors and standing condensate.

Slicing, bagging and packaging line

The high-speed bread slicer is the next process step after the cooler tunnel. Each slice generates a small flour and crumb dust release, and a Goodman Fielder Erskine Park scale slicer running thousands of loaves per hour generates substantial airborne crumb dust requiring dedicated local exhaust at 0.5 metres per second minimum capture velocity. The slicer extract routes to a dedicated crumb collection cyclone, separately from the upstream flour dust collector to prevent cross-contamination.

The bagging line generates polyolefin film dust and heat seal smoke from the heat seal jaws closing the bag. Separate exhaust capture at 0.3 to 0.5 metres per second over the heat seal jaws handles the smoke release. Polyolefin film smoke contains low concentrations of formaldehyde (1 ppm STEL under Safe Work Australia) and other volatile organic compounds, and dedicated exhaust through a thermal oxidiser or activated carbon filter is the standard discharge treatment.

The packaging line is the highest-hygiene production zone in the bakery and runs at plus 20 to plus 25 Pascals pressurisation relative to adjacent zones, with HEPA-filtered supply air at MERV 14 minimum. The Allergen Bureau VITAL allergen management programme requires positive separation between the bakery packaging zone and any allergen-containing parallel line (egg, peanut, tree nut, sesame and dairy are the principal Australian bakery allergens). Sealed-seam AS 4254 Class B or SMACNA Class A duct construction maintains the pressurisation cascade and the allergen separation.

Biscuit line ventilation — Tim Tam, Shapes and the Arnott's Huntingwood scale

The Arnott's Huntingwood NSW biscuit operation is the largest biscuit production facility in Australia and represents the most engineered biscuit HVAC envelope in the country. The Tim Tam line runs a 100 plus metre continuous tunnel oven at 200 to 240 degrees Celsius baking chamber temperature, a cooling tunnel of similar length, a chocolate enrobing line, a packaging and case-erect line, and a substantial flour, sugar and cocoa dust handling envelope upstream of the oven.

Biscuit tunnel oven exhaust

The biscuit tunnel oven exhaust is materially the same as a bread tunnel oven but at typically slightly lower baking chamber temperature (200 to 240 degrees Celsius versus 220 to 260 for bread) and at a much longer tunnel length (100 plus metres at Huntingwood). The exhaust stack ductwork is 316L stainless throughout with fully welded longitudinal seams. NFPA 86 governs the combustion air supply, flue gas extract and explosion relief on the gas train. Heat recovery economiser at the stack pre-heats the bakery hot water supply.

Chocolate enrobing line and cocoa dust extract

The Tim Tam chocolate enrobing line generates airborne cocoa dust on the enrober extract. The chocolate is melted, tempered and applied via the enrober tunnel, then cooled through a chocolate cooling tunnel before the final wrap and case-erect. The cocoa dust extract handles the Kst 100 to 130 St1 explosible dust load with full NFPA 68 deflagration venting, NFPA 69 isolation, bonding and grounding, conductive duct construction and routine clean-down. The chocolate enrobing line cooling tunnel runs at 10 to 15 degrees Celsius with controlled humidity at 40 to 60 percent RH to support optimal chocolate setting.

Biscuit packaging and Allergen Bureau VITAL

The Tim Tam packaging line runs adjacent to multiple other Arnott's biscuit product lines in the same Huntingwood facility, and the Allergen Bureau VITAL allergen management programme requires positive separation between allergen-containing and allergen-free parallel lines. The packaging zone runs at plus 25 Pascals pressurisation with HEPA-filtered supply air. Sealed-seam AS 4254 Class B or SMACNA Class A duct construction maintains the cascade. Arnott's exports Tim Tam to the United States, Canada, the United Kingdom and ASEAN under AQIS export licence, and the export market regulatory envelope adds further hygiene and allergen management documentation requirements.

Meat pie and pastry — the Four'N Twenty Bairnsdale envelope

The Four'N Twenty operation at Bairnsdale VIC is the largest dedicated Australian meat pie manufacturer and represents the most automated pie production envelope in the country. The Patties Foods Bairnsdale facility runs the integrated meat pie, party pie, sausage roll, pasty and frozen pastry production scope on multiple parallel lines. The HVAC engineering scope spans the bakery-style oven and pastry handling envelope, the meat-processing-style cold chain and IQF freezer envelope, and the substantial NFPA 96 deep-fry exhaust scope on the pie pastry frying stages.

Pie pastry preparation

Pie pastry preparation runs in the cold side of the plant at 4 to 8 degrees Celsius to maintain the pastry workability. Mixer extract, sheeter extract and the pastry handling envelope all run dedicated 316L stainless ductwork. The pastry pre-freeze stage at minus 25 to minus 35 degrees Celsius supports the downstream automated pastry handling (filling deposit, top sheet placement, crimping) without dough deformation.

Pie filling cooking and meat handling

The pie filling preparation runs adjacent to the pastry line with substantial meat handling (mince, vegetable, gravy preparation). The meat handling zone runs at 4 to 8 degrees Celsius with HEPA-filtered supply per the FSANZ 3.2.2 hygiene requirement and the AS 4696 meat processing standard cross-application. The filling cooking stage runs at 80 to 100 degrees Celsius with steam release captured under dedicated exhaust at 0.5 metres per second capture velocity.

Pie cooking ovens

The pie cooking stage runs continuous tunnel ovens at 200 to 230 degrees Celsius baking chamber temperature with NFPA 86 exhaust scope. Some operations additionally run deep-fry stages on certain pastry products (Cornish pasty, savoury pastry, sausage roll variants) at 175 to 195 degrees Celsius oil temperature, with NFPA 96 commercial kitchen grease-laden exhaust scope.

IQF and frozen storage

The finished cooked pie product moves through an IQF freezer at minus 30 to minus 40 degrees Celsius with air velocity 3 to 6 metres per second across the product to drive the rapid freeze required for individual pie freezing. R-717 ammonia refrigeration plant under AS/NZS 1677 supports the cold chain. Pre-insulated 316L stainless panel duct with vapour-tight seal at every penetration, condensate drain trays under supply diffusers, and door air curtain integration manage the IQF tunnel envelope.

Frozen distribution

The frozen storage and dispatch operates at minus 18 to minus 25 degrees Celsius with thicker panel insulation. Loading dock chilled airlock at 4 to 8 degrees Celsius with high-velocity air curtains at 1.5 to 2.5 metres per second maintains the cold chain integrity during truck loading per AS 4326. Mrs Mac's West Perth, Sara Lee Australia and Patrick's Pies all run materially the same pie production envelope as Four'N Twenty Bairnsdale, with site-specific variations in product mix and line configuration.

Mondelez Cadbury — the chocolate biscuit and confectionery envelope

The Mondelez Cadbury operations in Australia run the chocolate biscuit production (Tim Tam-equivalent product under Mondelez ownership, Mint Slice, Royal Dansk Danish butter cookie equivalents) and the broader chocolate confectionery line (Cadbury Dairy Milk, Cadbury Caramello, Cherry Ripe, Crunchie) on integrated facilities. The Hobart Cadbury plant is one of the largest chocolate manufacturing operations in the southern hemisphere.

The HVAC engineering scope at Mondelez covers the cocoa powder and sugar handling envelope at the Zone 21 hazardous area scale equivalent to the largest Australian flour mills, the chocolate melting and tempering line at 30 to 50 degrees Celsius with controlled humidity, the chocolate enrobing line for the biscuit and bar product, the chocolate cooling tunnel at 10 to 15 degrees Celsius, and the substantial packaging line with Allergen Bureau VITAL compliance. The cocoa dust deflagration risk is the principal Zone 21 hazardous area concern at the Mondelez operation, alongside sugar dust handling in the confectionery line.

SBKJ supplies the Mondelez cocoa and sugar dust extraction ductwork as 316L stainless via the SBAL-V auto duct line for rectangular sections and the SBFB-1500 spiral fitting forming line for round dust conveying duct. The dust collector housings and explosion isolation valve interface ductwork are fabricated using the SB-ZF1500 stitchwelder for fully welded TIG seam construction.

Allied Pinnacle and Manildra Group — the upstream flour mill scope

Upstream of the bakery and biscuit manufacturers sits the flour milling tier. The Allied Pinnacle Picton NSW operation is the largest Australian flour mill and represents the most demanding flour dust deflagration envelope in Australian food manufacturing. The Manildra Group Manildra NSW operation runs flour milling, wheat starch production and gluten production on an integrated site — the gluten and wheat starch dust handling envelope at Manildra is one of the highest-Kst dust scopes in Australian food manufacturing.

Flour mill silo and roller mill envelope

The Allied Pinnacle and Manildra flour mill operations run hundreds of tonnes per day of flour through silo, conveying, roller mill, sifter, purifier and bagging operations. Every step in the process is a Zone 21 hazardous area under AS/NZS 60079.10.2. The dust collector population at a major Australian flour mill exceeds 50 individual collectors covering different process steps. Each collector requires dedicated NFPA 68 deflagration venting, NFPA 69 isolation, bonding and grounding, conductive duct construction and routine clean-down.

Wheat starch and gluten — the elevated Kst envelope

The Manildra Manildra NSW operation runs wheat starch production and gluten production downstream of the flour milling. Wheat starch is essentially purified amylose and amylopectin and carries a Kst typically slightly higher than wheat flour, in the 120 to 160 range. Vital wheat gluten is the protein fraction of wheat and carries a Kst in the 110 to 150 range. Both are St1 to low St2 explosible dust with the same hazardous area implications as wheat flour, but with substantially higher Kst index at the upper end of the range. The Manildra Manildra dust extraction scope is one of the most demanding Zone 21 hazardous area duct packages in Australian food manufacturing.

SBKJ scope on flour mill projects

SBKJ supplies the flour mill dust extraction ductwork as 316L stainless via the SBAL-V auto duct line for rectangular sections, the SBFB-1500 spiral fitting forming line for round dust conveying duct, the SB-ZF1500 stitchwelder for the dust collector housing fabrication, the SBPC1500 plasma cutter in spark-resistant configuration for plate prep in the Zone 21 hazardous area, and the SBLR-600 longitudinal seam welder for large-section plenum and collector body fabrication. The SBSF-1525 round flanger produces the flanged terminations on the round conveying duct for connection to the isolation valves and conveying transitions.

Mauri ANZ and Lallemand Yeast — the baker's yeast supply tier

Australian baker's yeast production at the major suppliers Mauri ANZ and Lallemand Yeast Australia introduces a distinctive HVAC engineering scope. Baker's yeast is produced by aerobic fermentation of molasses or sugar substrate, with substantial CO2 evolution from the fermentation tanks and substantial airborne fungi load in the downstream drying and packaging operations. The cross-contamination risk to downstream bakery customers is significant if airborne fungi escape the producer's containment envelope.

The HVAC engineering response is HEPA-filtered supply at H13 grade across the fermentation, harvesting, drying and packaging operations, with full pressurisation cascade from clean (packaging plus 25 Pa) to dirty (fermentation tank vent minus 25 Pa). The fermentation tank vent gas is treated through a wet scrubber and biofilter to capture the CO2 and any volatile organic compounds before atmospheric discharge. Duct construction is 316L stainless throughout because the warm-humid fermentation environment generates aggressive corrosion in any galvanised duct.

Beerenberg, McCormick, Continental — allied food manufacturing scope

The allied food manufacturing operators — Beerenberg Hahndorf SA (jam and condiment), McCormick Foods Australia Geelong VIC (spice and seasoning), Continental Unilever (dry soup and prepared food mix), Bega Cheese Tatura VIC (Vegemite production acquired from Mondelez in 2017), Suntory Beverage & Food Schweppes — share HVAC engineering scope with the bakery sector at varying levels. Beerenberg jam production runs substantial steam and sugar load with dedicated capture exhaust over the cooking kettles. McCormick spice handling generates airborne spice dust including capsicum dust (Kst 50 to 80 St1 explosible), cinnamon dust (Kst 100 to 130 St1), and other Zone 22 hazardous area dust. Continental dry soup production handles bouillon, dried vegetable and starch dust. Bega Vegemite production runs the yeast extract concentration line with substantial steam evaporator load.

Suntory Schweppes and other beverage operations

Beverage operations at Suntory Schweppes Australia, while not strictly bakery, share substantial HVAC engineering scope with the bakery sector. CO2 dosing on the carbonated beverage line introduces a Zone 2 hazardous area dimension under AS/NZS 60079 with asphyxiation risk in the dosing room. Sugar handling on the syrup preparation line generates Zone 22 sugar dust with the same explosible dust implications as bakery sugar handling. The bottle filling and labelling line runs HEPA-filtered supply at plus 20 Pa pressurisation for FSANZ 3.2.2 compliance.

Materials specification — why 316L stainless is the bakery default

316L versus 304L in bakery

While 304L is the meat processing default, 316L is the industrial bakery default. The molybdenum addition in 316L (2 to 3 percent) resists chloride attack from coastal Australian sites and the trace chloride load in any food sanitation chemistry, and resists the acid-aerosol corrosion in the proofing room atmosphere (lactic and acetic acid vapour from sourdough levain culture) more aggressively than 304L. The bakery atmosphere also typically carries higher residual moisture than the meat processing environment due to the continuous steam release from cooling product, baking and proofing. 316L delivers a 20 to 25 year facility life on the bakery production-zone duct versus 12 to 15 years for 304L under the same conditions.

316L versus galvanised

Galvanised G275 ductwork is acceptable in industrial bakery facilities in isolated dry plant rooms with no chloride exposure and no direct flour dust exposure. Typical permitted zones are administrative office areas, dry electrical switch rooms, the boiler room (although the flue gas section is stainless), mezzanine plant rooms with positive pressurisation, and the boundary services ventilation around the building envelope. Outside those zones, galvanised is a 24 to 36 month replacement programme under the combined exposure of flour dust, sanitation chemistry, oven exhaust acid condensate and refrigeration plant ammonia load.

Carbon steel for silo and collector body

Carbon steel at 1.2 to 1.5 millimetre gauge is acceptable for the silo body and the dust collector body where the dust pressure rating drives the gauge specification. The clean-side post-collector ductwork is 316L. The silo body construction is heavier gauge (3 to 6 millimetres) to withstand the static head pressure of the bulk flour load and the design deflagration pressure.

Where 304L is acceptable in bakery

304L is acceptable on the dry side of the bakery operation — the mixer floor extract upstream of any humidity exposure, the office and dry plant room scope, and the loading dock scope. The premium for 316L over 304L is 15 to 25 percent on the duct fabric cost line, and the engineering decision is whether the long-term corrosion environment justifies the premium. For the wet side of the operation (cooler tunnel, proofing room, ammonia plant room), 316L is the default. For the dry side, 304L is acceptable.

Air change rates and ventilation calculation

Australian Standard 1668.2 sets the minimum outdoor air, exhaust rate and pressurisation differential per zone. The typical air change rate per zone in an industrial bakery is:

• Flour silo and bulk handling — continuous dust collector extract at 600 to 1200 cubic metres per hour per tonne of conveying capacity.
• Mixer floor and dough preparation — 15 to 20 air changes per hour with dedicated mixer hopper local extract.
• Continuous proofing tunnel — 8 to 15 air changes per hour with dewpoint-conditioned supply.
• Tunnel oven exhaust capture — dedicated NFPA 86 scope sized for burner heat release and process moisture release.
• Bread cooler tunnel — 20 to 30 air changes per hour with dedicated exhaust to handle moisture and aerosol load.
• Slicing and bagging — 20 to 30 air changes per hour with HEPA-filtered supply and dedicated local exhaust at the slicer.
• Biscuit cooling tunnel — 15 to 25 air changes per hour.
• Chocolate enrobing line — 10 to 20 air changes per hour with dedicated cocoa dust extract.
• Pie pastry preparation — 15 to 25 air changes per hour at 4 to 8 degrees Celsius.
• Pie filling cooking — 15 to 20 air changes per hour with dedicated steam capture.
• IQF tunnel — 30 to 60 air changes per hour with air velocity 3 to 6 metres per second.
• Frozen storage — 8 to 12 air changes per hour.
• Ammonia compressor room — 30 air changes per hour minimum under AS/NZS 1677 emergency ventilation.
• Deep-fry exhaust capture — dedicated NFPA 96 scope at 0.5 to 1.0 metres per second capture velocity.
• Loading dock — 8 to 12 air changes per hour with dock door air curtain integration.

The total facility outdoor air rate on a Goodman Fielder Erskine Park scale bread plant typically sits at 25 to 40 cubic metres per second of conditioned outdoor air, with the flour dust collector extract and the tunnel oven combustion air supply dominating the load. For an Arnott's Huntingwood scale biscuit operation the total outdoor air is comparable at 30 to 50 cubic metres per second equivalent, with the biscuit tunnel oven combustion air supply and the cocoa dust collector extract dominating.

Standards and regulatory references

Australian industrial bakery HVAC ductwork is governed by an overlapping set of standards and codes. The primary references that appear in every facility specification are:

• AS/NZS 60079.10.2 — Explosive atmospheres — Classification of areas — Combustible dust atmospheres. The principal hazardous area classification standard for flour, sugar and cocoa dust.
• AS/NZS 60079.14 — Electrical installations design selection and erection in explosive atmospheres.
• AS 3957 — Industrial dust hazard standard. Foundational Australian standard on combustible dust risk assessment and control.
• NFPA 660 — Standard for Combustible Dusts and Particulate Solids (2025 consolidation of NFPA 61 agricultural dust, NFPA 484 metal dust, NFPA 654 combustible particulate solids and NFPA 664 wood dust). The principal international reference for bakery dust deflagration management.
• NFPA 61 — Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities (now consolidated into NFPA 660 but historically the most-referenced US bakery dust standard).
• NFPA 654 — Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids (now consolidated into NFPA 660).
• NFPA 68 — Standard on Explosion Protection by Deflagration Venting.
• NFPA 69 — Standard on Explosion Prevention Systems.
• NFPA 86 — Standard for Ovens and Furnaces. The principal industrial oven exhaust standard for continuous tunnel ovens, rack ovens, rotating ovens and deck ovens.
• NFPA 96 — Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations. Governs deep-fry exhaust on donut, churro, savoury pastry and pie pastry operations.
• AS 1668.1 — The use of ventilation and air conditioning in buildings — Fire and smoke control.
• AS 1668.2 — The use of ventilation and air conditioning in buildings — Mechanical ventilation. Sets minimum outdoor air, exhaust rates and zone separation requirements.
• AS 4254.1 and AS 4254.2 — Ductwork for air-handling systems in buildings. Construction class, sealing class and leakage testing.
• AS/NZS 1677 — Refrigerating Systems. Safety, design and construction of ammonia and other industrial refrigeration plant.
• AS/NZS 5149 — Refrigerating Systems and Heat Pumps. Safety and environmental requirements.
• AS 1530.4 — Methods for fire tests on building materials and structures. Oven stack and dust collector duct fire integrity.
• AS 1851 — Routine service of fire protection systems and equipment. Oven exhaust fire suppression and deep-fry exhaust suppression.
• AS 4696 — Australian Standard for the Hygienic Production and Transportation of Meat and Meat Products. Cross-applied to meat pie and savoury pastry production.
• AS/NZS 4674 — Construction and fit-out of food premises.
• AS 4326 — The Storage and Transport of Frozen Meat and Meat Products. Cross-applied to frozen bakery and IQF pie product.
• AS 4775 — Emergency Eyewash and Shower Equipment. Ammonia compressor room emergency stations.
• AS 1657 — Fixed platforms, walkways, stairways and ladders. Access for oven and dust collector servicing.
• AS 1428.1 — Design for access and mobility under the Disability Discrimination Act.
• NCC Volume One Class 6, 7b and 8 — National Construction Code Class 6 retail bakery shop, Class 7b food storage, Class 8 industrial manufacturing classifications.
• FSANZ Food Standards Code 4.2.1, 4.2.2, 4.2.3, 4.2.4 and 3.2.2 — Food Standards Australia New Zealand. Hygiene, microbial, chemical residue, zoonotic and HACCP requirements.
• HACCP — Hazard Analysis and Critical Control Point. Foundational food safety methodology.
• ISO 22000 — Food safety management systems.
• AQIS export licence — Australian Quarantine and Inspection Service export licensing for Arnott's biscuit export to the United States, Canada, United Kingdom and ASEAN markets, Mondelez Cadbury biscuit export, Sara Lee Australia dessert export and Four'N Twenty pie export.
• Allergen Bureau VITAL — Voluntary Incidental Trace Allergen Labelling allergen management programme. Egg, peanut, tree nut, sesame and dairy are the principal Australian bakery allergens.
• Halal certification — AFIC, ICCV, HCAS and other Halal certifying bodies for Halal-certified bakery export to Middle East and ASEAN markets.
• Kosher certification — KA Kosher Australia, Council of Orthodox Synagogues for Kosher-certified bakery product.
• MSC certification — Marine Stewardship Council certification on any seafood-containing bakery product (some specialty pie and pastry product).
• Organic certification — Australian Certified Organic, NASAA Organic and other certification bodies for organic flour, sugar and bakery ingredient supply.
• MIA Meat Industry Australia — Meat Industry Association cross-applicable to meat pie and savoury pastry production.
• Safe Work Australia Workplace Exposure Standards — wheat flour 10 mg/m3 inhalable, 5 mg/m3 respirable 8-hour TWA; ammonia 25 ppm 8-hour TWA, 35 ppm STEL; CO2 5000 ppm 8-hour TWA, 30000 ppm STEL; CO 30 ppm 8-hour TWA; formaldehyde 1 ppm STEL; oil mist 5 mg/m3 8-hour TWA.
• ASHRAE Handbook — Chapter 22 Refrigerated Processing, Chapter 23 Bakery Products, Chapter 35 Drying and Dehumidification.
• ACGIH Industrial Ventilation Manual — Local exhaust ventilation design methodology.

SBKJ machinery for industrial bakery ductwork — sized for the full plant scope

Fabricating the duct schedule for an integrated industrial bread, biscuit, pastry or pie plant, a flour mill or a confectionery manufacturer touches the full SBKJ product range. Each machine has a specific role in the bakery duct fabrication scope.

SBAL-V auto duct line — 316L stainless variant (bakery default)

Our SBAL-V auto duct line is the workhorse of rectangular duct fabrication for HVAC contractors across 100+ countries. The 316L stainless variant is the standard configuration for the Australian industrial bakery sector, the biscuit and confectionery manufacturers, the flour milling tier and the meat pie and pastry producers. The SBAL-V is offered in models SBAL-V-1250J and SBAL-V-1500J, handles material thicknesses of 0.5 to 1.5 millimetres, with a maximum working width of 1,250 or 1,500 millimetres, at a forming speed of 16 metres per minute, with overall dimensions of 14,000 by 2,000 by 1,800 millimetres or 14,000 by 2,200 by 1,800 millimetres, requires 87 kilowatts, weighs approximately 16 tons, and runs on 380V 50Hz 3-phase. Hardened tooling for stainless coil, dedicated stainless decoiler, and adjusted forming pressures for the work-hardening characteristics of 316L are standard on the bakery-grade configuration. PLC control is Siemens or Mitsubishi standard. Welded longitudinal seam tooling is available as a factory option for HACCP-critical zones and Zone 21 hazardous area service — 4 to 6 weeks longer lead time but the standard for new bakery and biscuit facility builds and for flour mill dust extraction projects. See the SBAL-V product page, our SBAL-V versus SBAL-III comparison, and the full machines catalogue.

SBAL-III auto duct line — mid-range alternative for galvanised

The SBAL-III is the mid-range duct line for galvanised duct fabrication on the dry-side bakery scope (administrative areas, dry plant rooms, mezzanine plant rooms with positive pressurisation, building services ventilation). For new bakery facility builds where the duct fabricator is supplying both galvanised dry-side and 316L stainless wet-side duct, the standard configuration is one SBAL-V at 316L and one SBAL-III at galvanised, providing parallel forming capability across both material specifications.

SB-ZF1500 stitchwelder — critical for oven exhaust stack and dust collector housing

The SB-ZF1500 stitchwelder is critical to the bakery duct fabrication scope. The machine handles material thicknesses of 0.8 to 3 millimetres, with a working length of 100 to 1,500 millimetres, covering diameters from Phi-150 to Phi-1500, with overall dimensions of 2,500 by 1,000 by 2,350 millimetres, running on 380V 50Hz 3-phase. Three applications dominate the bakery scope: the continuous tunnel oven exhaust stack at 220 to 260 degrees Celsius where continuous TIG welded seams are essential under NFPA 86 high-temperature service, the dust collector housing on the flour, sugar and cocoa dust extraction scope where the Zone 21 hazardous area requires fully welded continuous seams, and the ammonia compressor room scrubber housing where the wet scrubber chemistry demands fully welded continuous seams in 316L stainless. The stitchwelder produces high-quality TIG seam welds at controlled current and travel speed. SBKJ engineers commission the stitchwelder to the buyer's nominated 316L coil specification at FAT.

SBSF-1525 round-duct flanger

The SBSF-1525 round-duct flanger forms connecting flanges on the ends of spiral duct sections and round fittings used throughout the bakery scope. Material handled is black steel 0.5 to 2 millimetres or stainless steel 0.5 to 2.5 millimetres, flanging width 75 to 152 millimetres, maximum weight capacity 360 kilograms, requires 2.5 kilowatts, weighs approximately 520 kilograms, with overall dimensions of 2,200 by 1,100 by 1,240 millimetres, runs on 380V 50Hz 3-phase. The SBSF-1525 produces the flanged spiral round duct used for the flour dust conveying line, the dust collector inlet and outlet, the proofing chamber supply, the cooler tunnel return air and the frozen storage room supply ductwork.

SBFB-1500 spiral fitting forming line

For spiral duct fittings (elbows, reducers, branch tees, taps) on the round-duct portion of the bakery project, the SBFB-1500 spiral fitting machine fabricates the corresponding fittings in matching diameter and material. Output diameters 80 millimetres to 1,500 millimetres; material galvanised, 316L stainless or 304L stainless to match the duct. The SBFB-1500 provides the fitting matching capability that pairs with the SBTF spiral tubeformer for the round dust conveying duct scope.

SBPC1500 plasma cutter — spark-resistant configuration for Zone 21 plate prep

The SBPC1500 plasma cutter prepares plate for plenum and large-section fabrication. Material galvanised, 316L stainless, 304L stainless or carbon steel up to 12 millimetres thick. Plasma cutting accuracy plus or minus 0.5 millimetre; edge quality suitable for direct TIG or MIG welding without secondary machining. The spark-resistant configuration is critical for plate prep work in the Zone 21 hazardous area dust collector fabrication, the ammonia compressor room scrubber housing and the bakery oven combustion zone — these are hazardous areas where the plasma cutter sparking is a documented ignition source if used inside the hazardous area envelope. SBKJ supplies the SBPC1500 with the spark-resistant tooling kit for hazardous area fabrication.

SBLR-600 longitudinal seam welder

For in-shop seam welding on rolled-and-formed duct sections, the SBLR-600 longitudinal seam welder produces continuous TIG seams on sections up to 6 metres long. Output suitable for the largest bakery plenum sections, the tunnel oven exhaust stack pre-assembly, the dust collector body fabrication and the ammonia compressor room scrubber discharge ductwork. The longitudinal seam welder is essential for the bakery scope where continuously welded seams replace stitch-welded or lock-seam construction in HACCP-critical zones and Zone 21 hazardous area service.

SBTF-1500 / SBTF-1602 / SBTF-2020 spiral tubeformers

The SBTF series spiral tubeformers fabricate the round spiral duct used throughout the bakery scope — flour conveying, dust collector ductwork, proofing chamber supply, frozen storage supply, ammonia compressor room exhaust and biscuit cooling tunnel air distribution. The SBTF-1500 covers diameters to 1,500 millimetres, the SBTF-1602 to 1,600 millimetres and the SBTF-2020 to 2,000 millimetres on the largest bakery scope. Material 316L stainless, 304L stainless or galvanised. The dust-tight construction option is standard on the bakery dust extraction scope — tighter lock seam geometry and additional sealant application during forming, suitable for the Zone 21 hazardous area conveying service.

The combined SBKJ machinery footprint for a major Australian bakery

The combined SBKJ machinery footprint for a major integrated Australian industrial bakery, biscuit plant or pie manufacturer project is typically: one SBAL-V at 316L stainless for the production-zone rectangular duct, one SBAL-III at galvanised for the dry-zone and dry-plant-room scope, one SBTF-1602 spiral tubeformer with multi-material capability (galvanised, 316L stainless), one SBFB-1500 spiral fitting machine, one SBSF-1525 round flanger, one SB-ZF1500 stitchwelder, one SBPC1500 plasma cutter (spark-resistant configuration), and one SBLR-600 longitudinal seam welder. The combined output capacity supports a 5,000 to 15,000 square metres per month duct fabrication rate, sufficient for the largest greenfield integrated bakery or biscuit plant build, or for the parallel SBKJ-supplied refit programmes at Goodman Fielder, Tip Top, Arnott's, Mondelez Cadbury, Four'N Twenty Bairnsdale and the major flour milling expansions at Allied Pinnacle and Manildra Group.

Common specification mistakes — what we see fail in the field

Mistake 1 — Galvanised G275 in flour dust extraction service

Galvanised ductwork in flour dust extraction service is a Zone 21 hazardous area non-conformance. The conductive earth path through galvanised duct is unreliable, the galvanising layer can create electrostatic accumulation under high-velocity dust flow, and the galvanising layer is not conductive enough to satisfy the AS/NZS 60079.14 bonding and grounding requirement. Specify 316L stainless or carbon steel throughout, with continuous TIG-welded longitudinal seams and verified earth continuity at every joint. We have inspected three Australian flour mill projects where the original duct contractor specified galvanised in the dust extraction scope and every project required full duct replacement to satisfy the hazardous area dossier.

Mistake 2 — Internally insulated tunnel oven exhaust stack

Bakery oven exhaust condensate (water vapour from product moisture release, plus combustion products from natural gas or LPG burner) saturates internal insulation within weeks of operation. The saturated insulation becomes fuel for the next stack fire and an audit non-conformance under NFPA 86 and AS 1851. Specify external insulation only on all oven exhaust ductwork. We have rebuilt two Australian bakery oven exhaust systems in the last five years where the original duct contractor specified internally insulated stack — every rebuild was triggered by a fire incident or an audit non-conformance.

Mistake 3 — Inadequate deflagration vent area on dust collector

Undersized deflagration vent area on a flour, sugar or cocoa dust collector permits the residual pressure (Pred) in the event of a deflagration to exceed the duct and collector pressure rating, resulting in catastrophic rupture rather than controlled venting. Vent area calculation per NFPA 68 Chapter 7 from the duct cross-section, length, dust Kst, ignition source location and pressure rating. Vent panels rupture-disc or hinged-door construction with rated burst pressure 0.1 to 0.2 barg. Vent panel discharge ducting routes to outdoor atmosphere with no obstruction and no occupied space within the discharge cone.

Mistake 4 — Missing or undersized explosion isolation between connected vessels

NFPA 69 explosion isolation valves on the inlet and outlet ductwork of the dust collector are mandatory to prevent flame and pressure propagation back to upstream silo or downstream conveying. Active isolation (fast-acting slide valve triggered by upstream pressure or flame detector) or passive isolation (back-pressure flap valve, rotary airlock with rated retention time) is sized per NFPA 69 Chapter 8. Missing isolation is the single most consequential dust collector explosion protection deficiency.

Mistake 5 — Galvanised ductwork in the ammonia compressor room

Galvanised steel under wet ammonia attack converts to zinc-ammonia complexes within months and the duct integrity is lost. The ammonia compressor room is a Zone 2 hazardous area under AS/NZS 60079 with a worker safety risk that demands 316L stainless ductwork throughout, spark-resistant motor and damper actuator construction, and continuous ammonia monitoring with two-stage alarm. Cost-engineering to galvanised in this room is a worker safety risk.

Mistake 6 — Shared HVAC return air across the pre-bake / post-bake hygiene zones

Return air ductwork that crosses between pre-bake (mixer, proofer, oven in-feed) and post-bake (cooler tunnel, slicer, packaging) hygiene zones is a documented cross-contamination vector and is a critical non-conformance under FSANZ 3.2.2 and HACCP audit. Specify dedicated supply and exhaust per zone at design stage; retrofitting separation costs 3 to 5 times the design-stage cost.

Mistake 7 — Internal duct insulation in the production zones

Internal insulation in any production-zone supply duct accumulates aerosolised flour, sugar, yeast and bakery enzyme over the production cycle and becomes a microbiological reservoir within the first sanitation cycle. The audit findings on Australian bakery plants over the last decade have repeatedly traced back to internally insulated ductwork. Specify external insulation only on all production-zone supply ductwork.

Mistake 8 — Insufficient capture velocity at the flour silo and mixer hopper

Flour dust capture velocity below 0.5 metres per second per the ACGIH Industrial Ventilation Manual permits airborne flour dust to escape into the working environment, increasing worker exposure above the 10 milligrams per cubic metre inhalable workplace exposure standard and increasing baker's asthma sensitisation risk. Verify capture velocity at commissioning with a calibrated thermal anemometer at every dust generation point.

Mistake 9 — Standing condensate in the bread cooler tunnel

Horizontal duct runs in the bread cooler tunnel without continuous slope to drain create standing water pools that become Listeria reservoirs and audit findings. Specify continuous 30 degrees minimum slope on all horizontal runs with drain tundishes at every low point and traceable drain routing to facility wastewater.

Mistake 10 — Galvanised support brackets on stainless duct

Galvanised threaded rod and galvanised brackets in contact with 316L or 304L stainless duct create galvanic cells at the contact line. The galvanised hardware corrodes preferentially and bleeds zinc onto the stainless surface, producing tea-staining that fails the AQIS export audit. Specify stainless support hardware throughout where stainless duct is installed.

Mistake 11 — Missing NFPA 96 fire suppression on deep-fry exhaust

Deep-fry exhaust on donut, churro, savoury pastry and pie pastry operations requires NFPA 96 wet chemical or water mist suppression integrated into the exhaust hood and the duct run. Suppression nozzles at the hood, at every 6 metre interval along the duct, and at the discharge fan inlet are the standard configuration. Annual servicing of suppression heads is non-negotiable under AS 1851.

Mistake 12 — Failing to integrate the loading dock cold chain on frozen pie

Cold chain failures under AS 4326 most often occur at the loading dock during the truck-loading window. Specify high-velocity air curtains at every dock door at 1.5 to 2.5 metres per second velocity, dock seal integration with the truck trailer body, and dedicated chilled supply at the dock-side. Loading dock HVAC failure is the most common AQIS dispatch verification non-conformance on frozen pie product.

Lead time, FAT and Australian dispatch from Box Hill North VIC

SBKJ's standard lead time for the 316L stainless variant of the SBAL-V auto duct line is 16 to 20 weeks from confirmed deposit to FAT-ready, plus 2 to 4 weeks domestic Australian dispatch from Box Hill North VIC to the customer site. The SBTF spiral tubeformer in 316L variant runs 12 to 16 weeks. The SB-ZF1500 stitchwelder for continuous TIG seam construction runs 10 to 14 weeks. The SBSF-1525 round-duct flanger runs 8 to 12 weeks. The SBFB-1500 spiral fitting machine runs 10 to 14 weeks. The SBPC1500 plasma cutter in spark-resistant configuration runs 10 to 14 weeks. The SBLR-600 longitudinal seam welder runs 8 to 12 weeks. Welded longitudinal seam tooling adds 2 to 3 weeks to the SBAL-V lead time. Mill certificate traceability to ASTM A240 or EN 10088-2 and third-party witnessed FAT add 1 to 2 weeks.

Factory Acceptance Test is run at the Box Hill North VIC office before dispatch with the buyer's nominated 316L coil specification and a full production cycle. We do not consider a bakery-grade machine ready to ship until the FAT report is signed against the contract performance specification. Buyers are welcome to attend the FAT in person or via live video link. The FAT covers tooling alignment, forming pressure on stainless coil, surface finish on the formed duct, seam quality on welded longitudinal seam variants, dimensional accuracy across the full forming envelope, dye penetrant test on the seam welds, conductive joint resistance measurement (critical for Zone 21 hazardous area duct), and a full single-shift production run with the buyer's coil.

Australian dispatch from Box Hill North VIC to the customer site is by Australian truck transport with ISPM-15 compliant crating where the machine is shipped via container, with humidity indicators, marine-grade desiccant and full all-risk transit insurance. Installation timing is coordinated with the customer's project programme. SBKJ engineers from the Box Hill North office attend the commissioning on site for 5 to 10 days for installation supervision, mechanical commissioning, electrical commissioning, operator training, hazardous area documentation handover and Performance Acceptance Test.

How SBKJ supports Australian industrial bakery customers

SBKJ Group operates from Box Hill North in Victoria, Australia, with engineering and after-sales support direct to the Australian industrial bakery, biscuit and confectionery, meat pie and pastry, flour milling and bakery ingredient sectors. Our typical customer engagement runs through five phases:

• Specification. Engineering review of the facility brief, zone-by-zone duct material and construction class recommendation, hazardous area scoping per AS/NZS 60079.10.2 dust atmospheres, machine sizing against the production volume targeted, integration with the AS/NZS 1677 ammonia plant scope, the NFPA 86 oven exhaust scope and the FSANZ 3.2.2 and AQIS compliance programmes.
• Quotation. Itemised landed-cost worksheet on EXW Box Hill North or delivered-to-site basis, with machine specification, FAT scope, training scope and spare-parts package.
• Order and FAT. 30 percent T/T deposit at order confirmation, 70 percent balance against dispatch documentation. FAT run with buyer's 316L coil before dispatch from Box Hill North.
• Installation and commissioning. 1 to 2 SBKJ engineers from the Box Hill North VIC office on site for 5 to 10 days for installation, mechanical commissioning, electrical commissioning, hazardous area documentation handover and operator training in English. Coordination with the customer's HACCP and AQIS programme owner.
• After-sales. 12-month warranty from commissioning, one-year wear-parts kit shipped with the machine, 72-hour remote support response from Box Hill North, 10-year-plus parts continuity guarantee.

Talk to an SBKJ engineer about your industrial bakery facility brief, your biscuit plant expansion programme, your meat pie line refit or your flour mill dust collector upgrade — we typically respond within 12 hours during Australian business hours. Contact SBKJ for an itemised landed-cost quote, or browse the full machines catalogue and the SBKJ Insights library for related guides. SBKJ Group is exhibiting at ARBS 2026 in Sydney in May, alongside the broader Australian HVAC trade and the Allied Pinnacle, Manildra Group and major bakery sector exhibitors.

The five highest-leverage decisions on an industrial bakery HVAC project

Across hundreds of Australian and export-market industrial bakery duct projects, the pattern we see is that the engineering scope is well understood — AS/NZS 60079, NFPA 660, NFPA 86, NFPA 96, FSANZ 3.2.2 and the AQIS export compliance programme are all documented — but integration is where projects succeed or fail. The five highest-leverage decisions:

1. Get the hazardous area classification right at design stage. The AS/NZS 60079.10.2 dust atmosphere classification report for the silo, conveying, sifter, mixer extract and dust collector is the foundational document that drives every downstream HVAC duct decision. Late changes to the hazardous area classification ripple through every duct package on the project and through the electrical installation under AS/NZS 60079.14. The hazardous area dossier should be the first deliverable on the project.
2. Specify 316L stainless throughout the wet-side and dust-extraction scope. Drawing the boundary between 316L stainless production-zone scope, 304L acceptable dry-side zones, galvanised dry-plant-room zones, and carbon steel silo and collector body is the largest single capital decision in the duct scope. Get it right at design stage, not after the AQIS auditor flags it on the routine cycle. The capex differential between an over-specified stainless-throughout solution and a properly zoned mixed-material schedule can be 20 to 30 percent on the duct fabric cost line.
3. Document the NFPA 68 deflagration venting and NFPA 69 isolation scope thoroughly. Dust deflagration is the single highest-consequence engineering hazard in any Australian industrial bakery or flour mill. The deflagration vent area sizing per NFPA 68, the explosion isolation valve selection per NFPA 69, the bonding and grounding earth grid resistance verification, and the routine clean-down programme are all critical. Late changes to the dust collector explosion protection ripple through every HVAC package on the project.
4. Specify FAT at the Box Hill North VIC office on every machine and every duct package. Compromised FAT correlates strongly with post-installation disputes. The cost of a thorough FAT is one week. The cost of skipping it is a rework cycle measured in months. SBKJ runs FAT at the Box Hill North VIC office on every machine with the buyer's nominated coil. The duct fabricator should run an equivalent acceptance test on the fabricated duct against the project specification before shipment to site, including conductive joint resistance measurement for Zone 21 hazardous area duct.
5. Plan the FSANZ 3.2.2 and AQIS commissioning around the audit cycle. The hygiene and allergen management envelope from mixer through to packaging is the AQIS auditor's principal concern outside the production-zone HVAC scope. Pressurisation cascade verification at every audit; Allergen Bureau VITAL allergen management verification at every product changeover; cold chain documentation programme for the frozen pie and frozen bakery product scope; routine flour dust clean-down audit on the secondary deflagration risk. Build the audit documentation programme into facility OPEX.

Get an itemised SBKJ quote for your industrial bakery, biscuit, meat pie or flour mill project →

FAQ

Why is flour dust deflagration the biggest hazard in an Australian industrial bakery?

Wheat, rye, oat, corn and rice flour all carry a Kst dust deflagration index in the 100 to 160 bar metre per second range, classifying as St1 to low St2 explosible dust under AS 3957 and NFPA 660. Any space where airborne flour dust can accumulate at or above 50 to 60 grams per cubic metre is a Zone 21 or Zone 22 hazardous area under AS/NZS 60079.10.2. The HVAC duct response is NFPA 68 deflagration venting, NFPA 69 explosion isolation, bonding and grounding, conductive duct construction, no internal insulation and routine clean-down.

What workplace exposure standard applies to wheat flour in an Australian bakery?

Safe Work Australia sets wheat flour at 10 milligrams per cubic metre 8-hour TWA inhalable, 5 milligrams per cubic metre respirable. Bakery enzyme aerosol drives occupational baker's asthma. The HVAC response is local exhaust at every dust generation point at 0.5 metres per second minimum capture velocity, dedicated dust collector ductwork separate from building general exhaust, and clean dilution supply at 25 to 30 air changes per hour over bench-work zones.

What temperature does a continuous tunnel oven exhaust run at?

Bread tunnel ovens at the major Australian plants run baking chamber 220 to 260 degrees Celsius. Exhaust stack 180 to 220 degrees Celsius at the canopy outlet, dropping to 80 to 120 degrees Celsius after dilution and heat recovery. Construction 316L stainless under NFPA 86, uninsulated to prevent insulation degradation, 30 degrees minimum slope on horizontal runs, fully welded longitudinal seams from the SBKJ SB-ZF1500 stitchwelder. Heat recovery economiser reduces gas demand by 15 to 25 percent.

What humidity does the proofing room require?

Bread proofing 30 to 40 degrees Celsius and 80 to 85 percent relative humidity for 45 to 90 minutes. Dewpoint-conditioned supply rather than room reheat. 316L stainless duct throughout because the warm-humid envelope plus acid aerosol from sourdough levain drives aggressive corrosion in galvanised duct. Air velocity at the dough surface 0.3 to 0.5 metres per second. CO2 from yeast fermentation exhausted continuously with monitoring alarm at 5000 ppm 8-hour TWA.

How does NFPA 96 differ from NFPA 86 in an industrial bakery?

NFPA 96 governs commercial kitchen grease-laden exhaust including deep-fry on donut, churro, savoury pastry and pie pastry. NFPA 86 governs industrial oven exhaust on the continuous tunnel oven, rack oven, rotating oven and deck oven banks. NFPA 96 demands grease-tight welded duct, integrated wet chemical or water mist suppression and slope to drain. NFPA 86 demands high-temperature stainless or refractory-lined duct, combustion air supply interlock and explosion relief. Many Australian bakeries run both standards in parallel.

What standards govern dust collector explosion protection?

AS/NZS 60079.10.2 hazardous area classification, AS 3957 dust hazard, NFPA 660 (the 2025 consolidated combustible dust standard), NFPA 68 deflagration venting, NFPA 69 explosion prevention. Minimum protective scope is deflagration vent panels on the collector body, explosion isolation valves on inlet and outlet, bonding and grounding to common earth grid, conductive duct construction, and continuous spark detection and quench on the upstream conveying.

What duct construction does the freezer plant on a meat pie line require?

Pie pastry pre-freeze minus 25 to minus 35 degrees Celsius. IQF finished cooked pie minus 30 to minus 40 degrees Celsius. R-717 ammonia under AS/NZS 1677. Pre-insulated 316L stainless panel duct with continuous vapour barrier on warm side, butyl gasket seals at every penetration, thermal-break hangers. Ammonia compressor room Zone 2 hazardous area with 30 air changes per hour emergency ventilation, wet scrubber discharge, continuous ammonia monitoring with alarm at 15 ppm.

What is the cocoa dust deflagration risk in an Australian biscuit plant?

Cocoa dust Kst 100 to 130 St1 explosible under AS 3957 and NFPA 660. Sugar dust 130 to 160 St1. Both minimum-explosible at 60 to 70 grams per cubic metre. Same Zone 21 or Zone 22 classification and same NFPA 68 / NFPA 69 protective scope as flour dust. Chocolate enrobing line generates cocoa dust on enrober extract requiring continuous extract and dedicated dust collector with full hazardous area compliance.

What pressurisation cascade does FSANZ 3.2.2 require?

Air flows from clean to dirty zones. Australian export-licensed bakeries build a multi-step cascade: final packaging plus 25 Pa, slicing and bagging plus 15 Pa, cooling tunnel plus 5 Pa, oven exhaust capture room neutral to minus 5 Pa, mixer and proofing minus 10 Pa, flour silo and conveying minus 15 Pa. AQIS and Allergen Bureau VITAL auditors verify with calibrated micromanometers. Sealed-seam AS 4254 Class B or SMACNA Class A duct construction.

What is the lead time for a bakery-spec SBAL-V in 316L stainless with hazardous area configuration?

SBAL-V 316L stainless with hazardous area extract configuration: 16 to 20 weeks from deposit to FAT-ready, plus 2 to 4 weeks Australian dispatch from Box Hill North VIC. SBFB-1500 spiral fitting 10 to 14 weeks. SB-ZF1500 stitchwelder 10 to 14 weeks. SBSF-1525 round flanger 8 to 12 weeks. SBPC1500 plasma cutter spark-resistant 10 to 14 weeks. SBLR-600 longitudinal seam welder 8 to 12 weeks. Welded seam tooling and Zone 21 hazardous area documentation add 2 to 3 weeks.