Coffee, Chocolate & Confectionery HVAC Ductwork Guide — Australian Boutique to Commercial Scale

Why coffee, chocolate and confectionery are one ductwork problem

At first glance, a 5 kg drum roaster in a Carlton laneway, a chocolate enrobing line in Ringwood, and a sugar panning drum in a Western Sydney confectionery plant look like three different worlds. They use different machinery, run on different shifts, sell into different retail channels, and serve different customers. From an HVAC ductwork perspective they are the same problem: a hot or aerosol-laden process stream that must be captured at source, conveyed through a clean, smooth, hygienically designed duct, scrubbed or oxidised where required, and exhausted to a permitted outlet without contaminating the food product, breaching the building envelope, or attracting an EPA notice.

Every food-process facility in Australia — boutique or commercial — answers to the same five-layer code stack. AS 1668.2 sets the mechanical ventilation rates and exhaust requirements. AS 4674 sets the food premises construction standard, including duct material and accessibility. FSANZ Food Standards Code 3.2.3 sets the food premises and equipment requirements at the federal level. HACCP from Codex Alimentarius drives the hazard analysis and critical control points. And EHEDG Doc 8 — the European Hygienic Engineering and Design Group guidance — defines the international benchmark for hygienic equipment and surfaces, including process ductwork. Where industrial roasters or large ovens are in play, NFPA 86 — the US National Fire Protection Association standard for ovens and furnaces — is the de facto international reference and is routinely cited by Australian insurers and consultant fire engineers on commercial roasting installations.

The single most expensive mistake we see Australian operators make is treating coffee, chocolate and confectionery duct as if it is the same as any commercial kitchen exhaust. It is not. Roaster exhaust runs hotter, chocolate conching releases cocoa butter aerosols that condense and oxidise on duct walls, sugar fume is mildly acidic and chlorides from CIP washdown destroy zinc within months. Galvanized duct fails fast in every one of these zones. The correct answer is stainless steel — 304 in the warm and ambient zones, 316L in the conching, tempering, enrobing, panning and caramel zones — fabricated to a hygienic finish that EHEDG would sign off on, and installed with cleanable joints, drain points at every low spot, and accessible inspection covers at every change of direction.

This guide walks the process map zone by zone — roastery first, then chocolate, then confectionery and sugar — calls out the temperature, humidity and hygiene profile of each, names the Australian operators we see in each segment, and finishes with the SBKJ machine configuration our customers use to fabricate this ductwork to a finish that passes a food safety auditor and a fire engineer on the same day.

Section 1 — The Australian code stack

Before any duct geometry is sketched, the engineer must confirm the code stack that the facility will be audited against. For coffee, chocolate and confectionery in Australia, that stack has five mandatory layers and one optional but strongly recommended international reference.

AS 1668.2 — The use of ventilation and airconditioning in buildings, Part 2: Mechanical ventilation in buildings

AS 1668.2 is the foundational mechanical ventilation standard in Australia. For food manufacturing it drives the minimum outdoor air rates per occupant, the local exhaust requirements for cooking and roasting equipment, the makeup air requirements to maintain pressure balance, and the duct construction class for fire and smoke control. For a roastery operating in a Class 8 industrial building, AS 1668.2 routinely intersects with the building's fire engineering report and the local council's mechanical services consent. For a chocolate factory or confectionery plant, AS 1668.2 sets the basic supply and extract framework on top of which the food-specific standards layer.

Cross-reference our AS 1668.2 reference guide for the duct construction class table, leakage limits and access requirements that apply across all food zones.

AS 4674 — Design, construction and fit-out of food premises

AS 4674 is the Australian Standard for food premises construction, and it is the document a council environmental health officer will inspect against on a fit-out approval. For HVAC ductwork it sets specific requirements: surfaces in contact with food or food preparation areas must be smooth, impervious, non-absorbent, easily cleanable and corrosion-resistant. Joints must be tight enough to prevent harbourage of food residue or pests. Ducts that pass over food preparation areas must be sealed and dust-tight, with no exposed flanges or threaded fittings that can shed debris into product below. The standard explicitly contemplates stainless steel and certain food-grade plastics for direct food contact surfaces, and excludes galvanized steel from areas subject to washdown.

FSANZ Food Standards Code 3.2.3 — Food Premises and Equipment

Food Standards Australia New Zealand publishes the Food Standards Code, and Standard 3.2.3 sets the federal-level requirements for food premises and equipment. The key clauses for HVAC ductwork: equipment must be designed and constructed to be easily cleaned and effectively sanitised; surfaces in contact with food must be smooth, impervious and non-toxic; and ventilation must be adequate to prevent excessive condensation or contamination. For state-licensed food premises — which includes virtually every commercial roaster, chocolate maker and confectioner in Australia — FSANZ 3.2.3 is enforced by the state food authority and by local council environmental health officers under the model Food Act.

HACCP — Codex Alimentarius and ISO 22000

HACCP — Hazard Analysis and Critical Control Points — originated with the Codex Alimentarius Commission of the FAO and WHO and is the international gold standard for food safety management. In Australia, most commercial roasters, chocolate makers and confectioners operate under a HACCP-based food safety programme, and many export-oriented operators are certified to ISO 22000, BRC or SQF — all of which build on the HACCP framework. For HVAC ductwork, the HACCP hazard analysis routinely identifies the following critical control points: condensate dripping from cool ducts onto product; airborne contamination of open product from contaminated supply air; foreign body contamination from corroding or shedding duct material; and microbiological growth on damp, soiled duct interiors. The duct design must address every one of these explicitly.

EHEDG Doc 8 — Hygienic Design Principles

The European Hygienic Engineering and Design Group is a consortium of equipment manufacturers, food industry players and research institutes that publishes the international benchmark for hygienic equipment design. EHEDG Doc 8 — Hygienic Design Principles — is the foundational document and covers material selection, surface finish, joint design, drainability and cleanability. For HVAC ductwork in direct or splash zones, EHEDG Doc 8 drives: 316L stainless steel as the default material, surface roughness Ra 0.8 micron or better on product-contact surfaces, fully welded seams with internal grinding and polishing, no crevices or dead legs, drainable geometry, and accessible inspection. Australian food safety auditors increasingly cite EHEDG conformance — particularly for export-oriented manufacturers — even though it is not formally part of the Australian code stack.

NFPA 86 — Standard for Ovens and Furnaces

For any commercial-scale coffee roaster, chocolate moulder with a tunnel oven, or industrial caramel cooker, NFPA 86 is the de facto international reference for fire and explosion protection. It applies to Class A ovens and furnaces — those heated to temperatures at or above the ignition point of the materials being processed. Coffee roasters operating with exhaust gas streams at 200 to 240 degrees Celsius and combustible chaff in the airstream sit squarely inside NFPA 86's scope. The standard drives requirements for purge cycles before ignition, interlocked safety controls, exhaust fan continuity, combustible-material handling and the design of the exhaust duct and stack. Australian commercial property insurers routinely require NFPA 86 conformance — or an equivalent — on new roastery installations as a condition of placing fire cover.

Section 2 — Coffee roasteries: from the laneway 5 kg drum to commercial 60 kg fluidised bed

The roaster as a process

A coffee roaster is, from a ventilation perspective, an indirect-fired or gas-fired oven that processes a combustible feedstock. Green coffee beans enter at ambient temperature, pass through a charge phase, drying phase, Maillard reaction phase, first crack at around 196 degrees Celsius, development phase, and second crack at around 224 degrees Celsius before being dumped to a cooling tray. Through the cycle the roaster exhaust gas stream pulls heat, moisture, smoke, volatile organics and a substantial mass of chaff — the dry papery skin shed by the bean as it expands — out of the drum and into the duct.

Drum roaster exhaust temperatures run at 200 to 240 degrees Celsius during the roast cycle, with brief excursions higher on the cool-down dump on some configurations. Hot air and fluidised bed roasters typically push exhaust temperatures slightly higher. Above 250 degrees Celsius, galvanized steel duct loses its zinc coating to spalling and rapid oxidation. The correct material is 304 stainless steel for the warm-side ductwork between the roaster and the cyclone or afterburner, and refractory-lined carbon steel — or a high-temperature stainless alloy — for the post-oxidiser stack where flue gas temperatures can exceed 250 degrees Celsius continuously.

Chaff and smoke control

Chaff is the single most common cause of roaster duct fires in Australian installations. Dry, low-density and combustible, chaff accumulates rapidly in any horizontal duct run, in elbows, in transitions, and in undersized cyclones. A 5 kg drum roaster typically sheds 100 to 150 grams of chaff per batch; a 30 kg commercial drum can produce 600 to 900 grams per batch. Over a six-month period without cleaning, an undersized duct can accumulate kilograms of chaff in the first elbow downstream of the cyclone.

The standard chaff control strategy is a primary cyclone immediately downstream of the roaster — sized for at least 90 percent capture at the design airflow — with a sealed chaff collection vessel emptied daily, and an inspection-accessible duct run downstream with no horizontal sections longer than three metres without a cleanout. Smoke and visible particulate that escapes the cyclone is the secondary problem. For inner-city installations, a secondary baghouse or wet scrubber, or an afterburner, is required to bring particulate emissions inside the state EPA limits.

NFPA 86 application to commercial roasters

NFPA 86 — Standard for Ovens and Furnaces — applies to commercial coffee roasters operated in the United States and is routinely cited as best practice by Australian commercial insurers and fire engineers. The standard drives a number of requirements that translate directly into duct design: a pre-ignition purge cycle to clear residual combustibles from the firebox and exhaust system; interlocked exhaust fan continuity to ensure the duct is always pulling when the burner is firing; exhaust duct construction in non-combustible material rated for the maximum operating temperature; isolation of the exhaust from any combustible building element with appropriate clearance and shielding; and an emergency vent path in the event of duct blockage. SBKJ ductwork specifications for roastery installations conform to NFPA 86 by default — 304 stainless on the warm side, refractory-lined steel on the stack, all-welded construction with no combustible gaskets, isolated from timber framing with the standard clearances.

Afterburner and thermal oxidiser selection

The single biggest planning consideration for an Australian commercial roaster operating in a mixed-use precinct is the secondary combustion device. Roaster exhaust contains a complex mix of volatile organic compounds — aldehydes, ketones, organic acids, pyrazines, furans — and visible smoke that, even after primary cyclone capture, exceeds the state EPA odour and particulate limits in inner-Melbourne, inner-Sydney and inner-Brisbane locations.

Two technologies dominate:

• Catalytic afterburner. A precious-metal catalyst bed operated at 300 to 400 degrees Celsius oxidises VOCs and smoke at low residence time. Energy consumption is modest because the operating temperature is low, and the catalyst can run on the latent heat of the roaster exhaust with a small auxiliary burner. The trade-off is that some chocolate roasters and dark-roast specialists generate exhaust loads that can poison the catalyst over time, requiring periodic catalyst replacement. Typical destruction efficiency is 95 to 98 percent on VOCs.
• Thermal oxidiser. A direct-fired chamber operated at 700 to 800 degrees Celsius destroys VOCs and smoke by full combustion. Energy consumption is higher because the operating temperature is higher, but the device is tolerant of high VOC loads and has no catalyst to poison. Destruction efficiency is 98 to 99 percent on VOCs. Regenerative thermal oxidisers — RTOs — recover heat from the combustion stream back to incoming exhaust and bring the energy penalty back into the catalytic range.

For boutique roasters at 5 to 15 kg batch size in standalone industrial sheds, neither device is typically required and the council issues development consent on the basis of the cyclone and stack height alone. For commercial roasters above 30 kg batch size or any installation in a mixed-use precinct, secondary combustion is effectively mandatory.

Green coffee bean storage

Green coffee bean storage is an often-overlooked but commercially important HVAC zone. Green coffee is hygroscopic — it picks up and releases moisture from ambient air — and the moisture content of the bean at the moment of charge into the roaster is one of the single largest variables in cup quality. Specialty roasters target green coffee at 10 to 12 percent moisture content, and they hold their green stocks at 18 to 22 degrees Celsius and 40 to 60 percent relative humidity to keep moisture content stable through the months between buying and roasting. The HVAC zone serving green storage is essentially a tempered, humidity-controlled warehouse — 304 stainless or galvanized supply ductwork is acceptable here because the air is dry and clean, and the temperatures are mild. Extract is modest and primarily for occupant comfort.

Australian coffee roasters — the operator landscape

Australia has one of the densest specialty coffee scenes in the world per capita, and the operator landscape spans every scale from single-barista 1 kg sample roasters to 200 kg commercial fluidised beds. The notable operators SBKJ engineers encounter in the Australian market include:

• ST. ALi Coffee (Melbourne). South Melbourne specialty roaster with multiple cafe outlets across Melbourne and Sydney; mid-scale drum roasters in a hospitality-precinct footprint, with sophisticated afterburner and odour control to meet inner-city council consent.
• Campos Coffee (Sydney). Newtown-headquartered specialty roaster with a national wholesale distribution and several flagship cafes; commercial drum roasters in an inner-Sydney warehouse footprint.
• Industry Beans (Melbourne). Fitzroy specialty roaster with a strong wholesale and direct retail operation; mid-scale drum roasters in an inner-Melbourne mixed-use precinct.
• Single Origin Roasters (Sydney). Surry Hills specialty roaster, one of the early specialty operators in Sydney; mid-scale drum roasters and a busy cafe.
• Padre Coffee (Melbourne). Brunswick East roaster with a wholesale-led business and multiple retail outlets; specialty drum roaster footprint in an industrial laneway environment.
• Toby's Estate (Sydney and broader). One of the larger Australian specialty roasters with international operations; multiple drum roasters at industrial scale.
• Allpress Espresso. Multinational specialty roaster originating in Auckland with significant Australian operations; commercial drum roasters in the Australian roastery footprint.
• Five Senses Coffee (Perth and Melbourne). Specialty roaster with a strong wholesale presence; commercial drum roasters at the Perth and Melbourne sites.
• Coffee Supreme (Australia and broader). Specialty roaster originating in Wellington with Australian operations; commercial drum roasters in mixed-use precincts.
• Genovese Coffee (Melbourne). One of the older Italian-heritage roasters in Melbourne with a substantial commercial production; large drum roasters at industrial scale.
• Vittoria Coffee. Major Italian-heritage commercial coffee operator with a large national distribution; commercial-scale production with all the associated secondary combustion and stack engineering.
• Lavazza Australia. Australian arm of the Italian multinational; commercial-scale roasting and distribution.
• Nespresso Australia. Australian arm of the global capsule coffee operator; predominantly distribution and capsule-handling, with associated packaging and warehouse HVAC.

These operators occupy three price-and-spec brackets. The boutique end runs single 5 to 15 kg roasters in industrial sheds with simple cyclone-and-stack ductwork. The mid-scale specialty end runs 30 to 60 kg roasters with afterburners or thermal oxidisers in mixed-use precincts. The commercial end runs continuous-process production with redundant exhaust trains, RTO heat recovery and full SCADA integration. SBKJ ships ductwork machinery for all three — the SBAL-V line in 304 or 316L stainless covers warm-side and ambient duct geometry, with a refractory-lined carbon steel option for the post-oxidiser stack on the same fabrication rig. For wider context on industrial fermentation and beverage process ventilation, see our companion guide on brewing, distilling and winery HVAC ductwork.

Section 3 — Chocolate manufacturing: conching, tempering, enrobing, moulding

The chocolate process in one sentence

Chocolate manufacturing starts with cocoa beans, processes them through cleaning, roasting, winnowing, grinding, conching, refining and tempering, then combines the chocolate mass with sugar, milk solids and other ingredients before moulding into bars, depositing into moulds, enrobing centres, or coating panned confectionery cores. From an HVAC ductwork perspective, four zones dominate the engineering: conching, tempering, enrobing and cooling. Each has a tight and unforgiving temperature and humidity profile, and each has a hygienic surface requirement that places 316L stainless steel at the centre of the specification.

Cocoa bean roasting

Cocoa bean roasting precedes the chocolate process proper and is, from a ventilation perspective, similar to coffee roasting at a slightly lower temperature — typically 110 to 140 degrees Celsius for the bean, with exhaust temperatures of 150 to 180 degrees Celsius. The same general principles apply: 304 stainless on the warm side, cyclone for husk capture, secondary combustion if required by EPA limits, and chaff management. For Australian operators who roast their own cocoa — including most of the bean-to-bar specialty makers — the cocoa roaster footprint is materially smaller than a coffee roaster but the engineering principles are the same.

Conching — the workhorse zone

Conching is the long, low-temperature mechanical agitation phase that develops chocolate flavour, smooths texture and drives off undesirable volatiles. The chocolate mass is held at 60 to 80 degrees Celsius and agitated continuously for 50 to 90 hours — sometimes longer for premium dark chocolate. Through the conche cycle, the chocolate releases a complex mixture of acetic acid, short-chain organic acids, water vapour, ethanol and other volatiles. These compounds carry distinct aromas — at the start of the cycle a sour, vinegar-like edge; through the cycle the sweeter, more refined chocolate aroma develops as the volatile acids are driven off.

The conching zone requires fume capture above the conche to remove these volatiles before they recirculate through the production area, condense on cool surfaces or contaminate adjacent process zones. The capture hood is typically located 200 to 400 millimetres above the conche aperture with a face velocity of 0.5 to 1.0 metres per second, ducted to a dedicated extract fan with a roof discharge clear of any building intake. The duct material is 316L stainless because the condensate is mildly acidic from the acetic acid load. Surface finish is Ra 0.8 micron or better internally to discourage build-up and allow CIP cleaning. Drain points at every low spot allow the condensate to be captured rather than puddling.

The adjacent room — where the operators work and where conched chocolate is sometimes blended or transferred — is held below 28 degrees Celsius to prevent the chocolate from over-softening when transferred. The supply ductwork serving the conching room is 304 stainless because there is no direct product contact, and the air change rate is typically 6 to 10 per hour.

Tempering — the tightest tolerance in food manufacturing

Chocolate tempering is the controlled crystallisation of cocoa butter into the stable beta-V polymorph, which gives finished chocolate its characteristic glossy surface, satisfying snap and resistance to bloom. The tempering process requires the chocolate mass to be cooled from working temperature down through a precise crystallisation window, then warmed slightly to dissolve any unstable polymorphs before depositing or enrobing.

The product specification is 30 to 32 degrees Celsius for dark chocolate and 29 to 31 degrees Celsius for milk chocolate, both with a tolerance of plus or minus 0.5 degrees Celsius across the working zone. This is the tightest temperature tolerance in mainstream food manufacturing — even sausage emulsion and bread proofing run wider. The HVAC engineering must support that tolerance not just at the chocolate, but at the surrounding air, the equipment surfaces, the operator's hands and tools, and the moulds or enrobing belt the chocolate contacts.

The standard tempering room HVAC specification is:

• Room dry bulb 18 to 22 degrees Celsius — cooler than the chocolate so that the surrounding environment supports cooling without forcing the cocoa butter into the wrong polymorph.
• Relative humidity 45 to 55 percent — low enough to avoid surface condensation on chilled equipment but high enough to prevent static dust attraction.
• Air change rate 8 to 12 per hour — sufficient to remove operator-generated heat and humidity without creating draughts.
• Supply air velocity at head height below 0.25 metres per second — to prevent surface skinning on chocolate held in open moulds or on the enrobing belt.
• Supply diffusion via swirl diffusers or perforated face diffusers — to spread air without point velocity.
• Duct material 304 stainless insulated externally with closed-cell elastomer or rigid mineral wool inside a stainless cladding — to prevent condensation in summer when the duct surface is below room dewpoint.
• Internal duct surface to a smooth, cleanable finish — Ra 1.6 micron or better — with all-welded seams in the working zone and accessible inspection covers at every change of direction.

Outside the tempering specification, the chocolate fails. Bloom — the dull, dusty surface that develops when the wrong polymorph crystallises — is the single most common visible defect on under-engineered Australian chocolate lines. The HVAC ductwork is half the answer; the other half is the temperer itself and the operator practice.

Enrobing — keeping the dust out

Enrobing is the application of a chocolate coating over a confectionery centre — a wafer, biscuit, nougat, caramel or panned nut — by passing the centre through a curtain of tempered chocolate. The chocolate must hit the centre at the same 30 to 32 degrees Celsius tempering window, and the surrounding environment must be free of dust, foreign body and excessive draught.

The enrobing zone HVAC specification follows the tempering specification on temperature and air movement, with additional requirements:

• Filtration on supply air to F8 or H10 — well above the typical food premises filter class — to prevent dust deposition on the wet chocolate surface.
• Local exhaust at the enrobing belt exit — to capture the trace cocoa butter aerosol that lifts off the wet surface and the trace dust kicked up by the moving belt.
• Pressure balance: enrobing zone slightly positive relative to surrounding rooms — to prevent infiltration of dust and foreign body from less clean adjacent zones.
• Duct material 316L stainless for the local exhaust because cocoa butter aerosol condensate is mildly acidic.
• Duct material 304 stainless for the supply because the air is filtered and clean.

Cooling tunnel — controlled crystallisation

After enrobing or moulding, the chocolate enters a cooling tunnel where the temperature is controlled at 8 to 12 degrees Celsius for the time required to set the cocoa butter into the stable beta-V polymorph. Too cold — below 6 degrees Celsius — and the chocolate sets too fast, freezing in unstable polymorphs that bloom later. Too warm — above 15 degrees Celsius — and the chocolate sets too slowly, breaking the moulding line continuity and developing a dull finish.

The cooling tunnel HVAC specification:

• Tunnel air temperature 8 to 12 degrees Celsius with a tolerance of plus or minus 1 degree across the tunnel length.
• Air velocity in the tunnel 0.5 to 1.5 metres per second along the belt direction — high enough to extract latent heat from the chocolate, low enough to avoid surface ripple.
• Relative humidity in the tunnel controlled below 60 percent to prevent surface condensation as the chocolate exits at near-tunnel temperature.
• Tunnel construction sealed and insulated — typically a sandwich panel structure with 304 stainless internal faces, served by 304 stainless insulated ductwork.
• Supply diffusion through linear slot diffusers along the tunnel length to ensure even temperature without local hot or cold spots.

Moulding and dispatch

Downstream of cooling, finished bars or moulded product enters a packaging hall typically held at 18 to 22 degrees Celsius and 45 to 55 percent relative humidity — the standard ambient food packaging specification. The HVAC ductwork here is 304 stainless for the supply and extract, or galvanized in very dry, infrequently washed zones. The hygiene burden drops materially because the chocolate is now sealed inside its wrap.

Australian chocolate manufacturers — the operator landscape

Australia has a layered chocolate manufacturing sector — major multinationals at one end, premium domestic brands in the middle, and a growing bean-to-bar specialty segment at the boutique end. The notable operators SBKJ engineers encounter in this market include:

• Cadbury Australia (Mondelez International). The Hobart factory is the largest chocolate manufacturing site in Australia and one of the largest in the southern hemisphere, with a long history dating from the 1920s. Mondelez also operates the Ringwood site in Victoria, which produces Cadbury and other confectionery lines.
• Lindt & Sprungli Australia. The Swiss premium chocolate maker operates a substantial Australian distribution and limited domestic production, with the global manufacturing footprint serving Australian retail.
• Haigh's Chocolates (Adelaide). Australia's oldest family-owned chocolatier, with a flagship factory in Parkside, Adelaide, and a national retail network. Bean-to-bar production at premium scale.
• Koko Black (Melbourne). Premium Australian chocolate maker with a flagship factory in Melbourne and a national boutique retail footprint.
• Whittakers (NZ). New Zealand premium chocolate maker imported into Australian retail at scale; not domestic Australian production but a major presence in the Australian retail set.
• San Churro. Chocolate and Spanish-style dessert chain with national footprint; operational ductwork sits more in the commercial kitchen exhaust segment than industrial process.
• Pana Organic (Melbourne). Premium organic chocolate maker with a Richmond production footprint.
• Loving Earth (Melbourne). Premium raw and organic chocolate maker with a Brunswick production footprint.
• Bahen & Co (Margaret River, WA). Boutique bean-to-bar maker with a small but highly regarded production at premium price point.

For boutique single-origin chocolate makers, the trend toward bean-to-bar adds the cocoa roasting zone back into the engineering scope — a smaller-scale equivalent of the coffee roaster discussion above. ASW — Australian Single Origin Whisky — has analogues in the bean-to-bar segment where single-origin cocoa is roasted, winnowed and ground on the same site as the chocolate manufacturing, requiring the full code stack to be addressed in a footprint half the size of a commercial operation.

Section 4 — Confectionery: panning, caramel, sugar, packaging

The confectionery process map

Confectionery is a broad category covering everything from boiled sugar lollies, gummies and jellies, through licorice, fudge, fondant and nougat, to chocolate-coated confectionery and panned dragee. From an HVAC perspective, four distinct zones dominate the engineering: sugar cooking, caramel cooking, sugar panning, and confectionery packaging.

Sugar cooking — the workhorse of confectionery

Sugar cooking is the process of dissolving sugar in water, then boiling off water to concentrate the sugar to the required Brix and temperature for the finished product. Hard candy is cooked to 150 to 160 degrees Celsius, fondant to 115 to 118 degrees Celsius, fudge to 113 to 116 degrees Celsius, and caramel anywhere from 140 to 170 degrees Celsius depending on the colour and texture target.

Through the cook, the kettle releases a substantial mass of water vapour with traces of caramelised sugar — a mildly acidic, sticky aerosol that condenses readily on cool surfaces. The capture hood above the sugar kettle is typically 316L stainless to handle the acidic condensate, with a face velocity of 0.5 to 1.0 metres per second, a fully-welded interior, and drain points at every low spot in the downstream duct. The duct must be sloped a minimum of 1 in 50 toward the drain points to prevent puddling of the sticky condensate, which oxidises and caramelises on the duct interior over time if allowed to stand.

Caramel cooking — high humidity, sugar fume

Caramel cooking is a variant of sugar cooking with cream, butter or other dairy added — and the dairy fat content materially changes the fume profile. The water vapour carries higher concentrations of milk solids and trace lactose, both of which deposit on cool duct interiors as a yellowish-brown film that requires regular CIP cleaning. The duct material is 316L stainless throughout the capture and extract train, and the CIP frequency is set by the production schedule and the auditable cleanliness verification programme — typically weekly during continuous production.

Sugar panning — the dragee process

Sugar panning is the process of building a sugar shell on a confectionery core — typically a nut, gum centre, raisin or chocolate centre — by rotating the core in a panning drum while spraying syrup and dusting with powdered sugar. The build cycle can take 4 to 24 hours depending on the shell thickness, and through that cycle the pan releases a continuous fine sugar dust that escapes the drum aperture into the surrounding room.

The panning room HVAC specification:

• Local dust extract at the pan rim with a capture velocity of 1.0 to 2.0 metres per second, ducted to a bag filter or cyclone before discharge — typically a baghouse for the fine sugar dust load.
• Room ambient at 18 to 22 degrees Celsius and 40 to 50 percent relative humidity — controlled humidity is critical because panning syrup viscosity is humidity-sensitive and the shell thickness uniformity depends on stable humidity through the build.
• Duct material 316L stainless because sugar dust deposit combined with humidity forms a mildly acidic film on duct interiors.
• Cleanout access at every change of direction because the dust load on the duct interior is heavy and routine inspection is required.

Confectionery packaging — ambient HVAC

Downstream of the cooking and forming zones, finished confectionery enters a packaging hall held at 18 to 22 degrees Celsius and 45 to 55 percent relative humidity — the standard food packaging ambient. The duct material here is 304 stainless for direct food zones and galvanized acceptable in zones with no washdown or direct product exposure. The hygiene burden drops as the product is sealed inside its wrap, and the engineering focus shifts to comfort, dust control and pressure balance with adjacent zones.

Australian confectionery operators

Australia has a long history of confectionery manufacturing with a mix of major multinationals and domestic brands. Notable operators in the Australian market include:

• Allen's (Nestle). Major confectionery brand owned by Nestle Australia, producing classic Australian lolly lines.
• The Natural Confectionery Co (Mondelez). Premium confectionery brand owned by Mondelez Australia.
• Lagoon Confectionery. Australian-owned confectionery manufacturer with a Melbourne footprint.
• Pascall (Nestle). Classic confectionery brand owned by Nestle, with a heritage in marshmallows and traditional confectionery.
• Darrell Lea (Quadrant). Iconic Australian confectionery brand owned by Quadrant Private Equity, with manufacturing footprint in NSW.
• Fyna Foods. Australian-owned confectionery manufacturer producing licorice and traditional Australian lollies.
• RJ's Licorice (NZ). New Zealand licorice maker with substantial Australian retail presence.

Sugar processing — the upstream feedstock

For completeness, the upstream sugar processing sector that supplies the confectionery and chocolate industry deserves a brief note. Australia is one of the world's larger sugar producers with the cane industry concentrated in Queensland and northern New South Wales. Notable operators include:

• Sugar Australia (Wilmar). One of the largest sugar refiners in Australia, with refineries in Yarraville (Victoria) and Mackay (Queensland).
• Sucrogen. Major sugar miller and refiner.
• CSR Sugar. Legacy name in Australian sugar — the sugar business was demerged from CSR Limited and now sits within Wilmar's Sugar Australia.

Sugar refinery HVAC engineering is a substantially heavier industrial application than confectionery — boiling pan extract, evaporator vapour, dryer exhaust — and is outside the scope of this boutique-to-commercial confectionery guide. However, the same material selection principles apply: 316L stainless for direct product contact and sugar fume, 304 stainless for general food zone, and carefully drained duct geometry to manage condensate.

Section 5 — Why galvanized fails in these environments

The three failure modes

Galvanized steel — carbon steel with a hot-dipped zinc coating — is the workhorse material for general commercial HVAC ductwork in Australia. It is cheap, easy to fabricate, and durable in dry, low-corrosion environments. In coffee, chocolate, confectionery and sugar zones, three failure modes destroy it inside one to three years of service.

Failure mode 1 — Heat at the roaster

The zinc coating on galvanized steel begins to oxidise rapidly above 200 degrees Celsius and spalls — flakes off — at sustained temperatures above 250 degrees Celsius. Roaster exhaust at 200 to 240 degrees Celsius is right at the boundary, and any local hot spot or transient excursion above 250 degrees Celsius accelerates failure. Once the zinc is gone, the underlying carbon steel oxidises rapidly and the duct integrity is compromised within months. The correct material on roaster warm-side duct is 304 stainless steel; on the post-oxidiser stack where temperatures can run 300 to 400 degrees Celsius continuously, refractory-lined carbon steel or a high-temperature stainless alloy is required.

Failure mode 2 — Sugar vapour and humidity

Sugar vapour and the trace organic acids in chocolate conching fume condense on cool duct interiors as a mildly acidic film. Combined with the humidity in conching, tempering and sugar cooking zones, this film attacks the zinc coating from the inside, stripping it within months. The corrosion is invisible on the outside of the duct but evident on the inside as a pitted, blackened surface that sheds particulate into the airstream — which then deposits on food product or equipment downstream. The correct material is 316L stainless for chocolate process and sugar fume zones.

Failure mode 3 — CIP washdown chlorides

Modern food-grade CIP detergents — clean-in-place chemistries used for the routine wash cycle on processing equipment — contain chloride salts that aggressively attack zinc. Even occasional washdown overspray onto duct exteriors will, over a year or two, strip the zinc coating in patches and expose the underlying steel. The duct then rusts visibly, sheds particulate into the airstream, and becomes a non-conformance on the next food safety audit. The correct material is 304 stainless for general food zone duct with any washdown exposure, and 316L stainless for direct product splash zones where the chloride load can be heavier.

Why stainless is the only durable answer

Stainless steel solves all three failure modes simultaneously. 304 stainless tolerates sustained service to roughly 250 degrees Celsius, resists humidity and acidic condensate adequately for warm-side roaster and general food zones, and tolerates chloride exposure at typical CIP concentrations. 316L stainless adds 2 to 3 percent molybdenum, which dramatically improves chloride pitting resistance and acidic condensate tolerance — making it the correct choice for chocolate conching and tempering, enrobing, sugar panning, caramel cooking and any zone with heavy CIP exposure. EHEDG Doc 8 specifies 316L as the default hygienic equipment material globally, and Australian export-oriented food manufacturers increasingly align with this standard regardless of formal AS or FSANZ requirements.

The cost premium of stainless over galvanized at fabrication is real — typically 2.5 to 4 times the material cost — but the lifecycle premium is negative. Galvanized duct in these zones is replaced every 18 to 36 months; stainless duct is replaced every 15 to 25 years. The lifecycle stainless solution is cheaper by a factor of 3 to 5 once replacement labour, food safety non-conformance cost and production downtime are included.

Section 6 — SBKJ machine configuration for this market

The fabrication problem

Australian fabricators serving the coffee, chocolate and confectionery sector face a specific machinery challenge: they need to fabricate ductwork in 304 and 316L stainless steel, to a hygienic standard that passes EHEDG and food safety audit, in geometries that include round, rectangular and oval cross-sections, with TIG welded seams to a smooth internal finish, and with the flexibility to switch between gauges and grades from job to job. Conventional Pittsburgh-seam galvanized duct lines do not do this. Mass-production rectangular duct lines configured for thin-gauge galvanized do not do this. The fabricator needs a line specifically configured for stainless food-grade work.

SBKJ SBAL-V — the stainless food-grade configuration

SBKJ ships the SBAL-V auto duct production line in a specific configuration for food-grade stainless work. The headline differences from the standard galvanized SBAL-V are:

• Stainless-compatible tooling. All forming rollers, shear blades and coining tools are specified in tool steel with PVD-coated working faces to prevent galvanic transfer to the stainless coil — a contamination risk on standard tooling configured for galvanized.
• TIG seam welder integration. The line integrates a TIG seam welding station to produce continuous, smooth, ground-finishable longitudinal seams in 304 and 316L coil from 0.8 to 2.0 millimetres. Pittsburgh and snap-lock seams are available where the food zone tolerates them, but the TIG seam is the default for direct food contact and product splash zones.
• Stainless-grade run-out tables. The run-out tables are stainless-faced or coated to prevent steel-on-stainless contamination during finished-duct handling.
• Coil interchange between 304 and 316L. The line is configured with a quick-change coil pay-off to allow a fabricator to switch grades within a shift — a common requirement on bespoke food-zone work.
• Refractory-lined carbon steel option. For roaster stack work above 250 degrees Celsius, the same SBAL-V rig can fabricate carbon steel duct geometry that is then refractory-lined on a downstream station. The refractory lining is a separate process and not part of the SBAL-V fabrication, but the duct geometry is compatible.
• Surface finish inspection. The line includes an in-line surface roughness inspection station to verify Ra 0.8 micron or better on the internal seam — the EHEDG default for hygienic direct food contact.

Site footprint and utilities

The SBAL-V stainless configuration occupies a similar floor footprint to the standard galvanized SBAL-V — typically 18 by 6 metres for the line plus a coil decoiler and finished-duct handling area. Utilities are similar: 50 kW electrical load, 6 bar compressed air, hydraulic oil reservoir. The TIG welder adds an inert gas supply (argon or argon-helium blend) and a higher local exhaust requirement at the welding station for the welding fume.

Fabrication standard delivered

An SBKJ SBAL-V line in food-grade configuration, run by a competent operator, delivers the following standard:

• 304 or 316L stainless steel duct in round, rectangular or oval cross-section.
• Length tolerances to plus or minus 1 millimetre per metre.
• TIG-welded longitudinal seam, internally ground and polished to Ra 0.8 micron or better.
• Drain points at every low spot on sloped runs.
• Crevice-free flange connections with food-grade EPDM gasket.
• Accessible inspection cover at every change of direction.
• Surface finish externally either No. 4 brushed or 2B mill finish per buyer preference.

This standard passes Australian food safety audit, EHEDG hygienic design verification, FSANZ 3.2.3 compliance check and the typical Australian commercial property insurer review for fire-rated stack work.

For background on the broader food-zone HVAC engineering context across multiple sectors, see our food processing industry guide, and for the cold-chain side of the chocolate cooling tunnel and confectionery packaging chain see our cold storage and cold chain HVAC guide.

Section 7 — Installation, commissioning and post-installation verification

For a typical commercial chocolate or coffee facility fit-out, the ductwork sequence runs: confirm slab levels and roof openings; lock process equipment positions (conche, roaster, temperer, enrober, tunnel, packaging) before drawing duct geometry; fabricate off-site or on-site as project size dictates; install on engineered supports with anti-vibration mounts at process equipment connections; insulate the cooling tunnel and tempering room duct and refractory-line the post-oxidiser stack; install fans and air handlers with flexible joints; commission with airflow balance, leak test, temperature and humidity verification, and surface swab on hygienic zones; hand over with as-built drawings, commissioning report and food safety officer sign-off.

The Factory Acceptance Test on 316L food-zone duct covers dimensional inspection against drawings, visual weld inspection every linear metre, internal surface roughness with a portable gauge, leak test at 1.5 times design pressure with smoke detection, drainability check, and witness by the customer's food safety officer. The Site Acceptance Test verifies airflow balanced within 10 percent of design, pressure differentials between rooms (tempering and enrobing slightly positive), temperature and humidity stable in tempering, enrobing, cooling tunnel and panning rooms, and bioburden swab on hygienic duct interiors before first product run.

Ongoing CIP and inspection follow a documented schedule: visual dry inspection at every change of direction at the HACCP-plan frequency (typically weekly during continuous production); wet CIP on direct food contact and product splash zones at typically weekly to monthly intervals; documented sign-off by named operator archived for audit; annual third-party hygienic inspection on premium operators with replacement of any duct section showing accelerated wear, pitting or build-up.

Section 8 — Worked example: a Melbourne bean-to-bar facility

A premium Australian chocolate maker plans a new bean-to-bar production facility in inner-suburban Melbourne — a 35 kg cocoa roaster, 250 kg conche, 100 kg temperer, enrobing line, cooling tunnel and packaging hall. The site is in a mixed-use precinct and requires council development consent. The customer wants to pass FSANZ 3.2.3, AS 4674, HACCP audit and EHEDG hygienic design verification, and to position the brand for export to premium retail in the EU and Japan.

The ductwork scope splits into seven sub-systems: 304 stainless warm-side roaster duct from roaster outlet through cyclone to thermal oxidiser inlet (12 m); refractory-lined carbon steel post-oxidiser stack to roof discharge with height to AS 1668.2 dispersion modelling (18 m); 316L stainless conching fume capture with drain points (14 m); 304 stainless insulated tempering room supply and extract (22 m combined); 304 stainless filtered F8 enrobing supply with 316L stainless local exhaust at belt exit (18 m combined); 304 stainless insulated cooling tunnel HVAC (16 m); 304 stainless packaging hall HVAC (40 m).

All 316L sub-systems fabricated on an SBKJ SBAL-V stainless food-grade line with TIG seam welding and internal grinding to Ra 0.8 micron. All 304 sub-systems fabricated on the same line to Ra 1.6 micron. Stack fabricated in carbon steel geometry then refractory-lined at a downstream station. The handover compliance pack covers AS 1668.2, AS 4674, FSANZ 3.2.3, HACCP, EHEDG Doc 8 hygienic design verification, NFPA 86 roaster compliance, council odour modelling, FAT and SAT reports, as-built drawings, weld procedure records and operator manuals. For a project of this scale — roughly 140 linear metres of food-grade duct — the fabricated ductwork represents one of the largest single fit-out line items. The lifecycle benefit is decisive: the duct outlasts the first generation of process equipment, passes audit on day one and every audit thereafter, and supports an export-quality brand position into the most demanding international retail channels.

Closing — the SBKJ position

The Australian coffee, chocolate, confectionery and sugar processing sectors share a single ductwork engineering problem at multiple scales. The code stack is well-defined — AS 1668.2, AS 4674, FSANZ 3.2.3, HACCP, EHEDG Doc 8 and NFPA 86. The material selection is clear — 304 stainless for general food zone and warm-side roaster, 316L stainless for chocolate process and sugar fume zones, refractory-lined steel for post-oxidiser stack. The fabrication standard is well-understood — TIG-welded seams, internally ground and polished to a hygienic finish, crevice-free flange connections, drain points and inspection access.

SBKJ Group, headquartered in Box Hill North, Victoria, ships HVAC duct fabrication machinery — including the SBAL-V auto duct production line in stainless food-grade configuration — to Australian and regional fabricators serving this market. Our engineering team in Australia and at our manufacturing facility supports specification, commissioning, training and ongoing service. Our customers fabricate the ductwork that ends up in the roasteries, chocolate factories, confectionery plants and sugar refineries that supply Australian consumers and increasingly support Australian premium food export.

If you are planning a new facility, expanding an existing line, or replacing duct that has reached the end of its galvanized service life, the right conversation starts with the process map and the code stack. Send us your process flow diagram and your facility floor plan, and one of our engineers will walk through the zone-by-zone material selection and fabrication scope with you.

Get an engineering review of your coffee, chocolate or confectionery duct scope →

FAQ

Why does galvanized ductwork fail in coffee roasteries and chocolate factories?

Three failure modes destroy galvanized in these environments. At the roaster, exhaust gases run 200 to 240 degrees Celsius — above the safe service temperature of zinc-coated steel. In chocolate and sugar zones, condensing sugar vapour combines with humidity to form a mildly acidic film that strips zinc from the inside. And chloride content in food-grade CIP detergents pits galvanized steel rapidly. Stainless 304 for general food and 316L for chocolate process and sugar zones is the only durable answer.

What temperature does coffee roaster exhaust ductwork need to handle?

Drum roaster exhaust runs 200 to 240 degrees Celsius with brief spikes higher. NFPA 86 applies to industrial roasters in this class and drives a refractory-lined steel stack design downstream of any afterburner, where flue gas temperatures can exceed 250 degrees Celsius. SBKJ specifies 304 stainless for warm-side roaster ductwork below 250 degrees and refractory-lined carbon steel for the post-oxidiser stack.

What is the tempering room HVAC tolerance for chocolate manufacturing?

Chocolate tempering requires 30 to 32 degrees Celsius plus or minus 0.5 degrees across the working zone. Outside that window the cocoa butter crystals form the wrong polymorph and the chocolate blooms. Air change rates of 8 to 12 per hour with low-velocity diffusion below 0.25 metres per second at head height prevent surface skinning. SBKJ ductwork for tempering rooms uses insulated 304 stainless with cleanable internal liners.

Do Australian coffee roasteries need afterburners or thermal oxidisers?

For commercial-scale roasters in built-up inner-city sites, yes. Roaster exhaust contains VOCs, smoke and chaff that exceed state EPA limits without secondary combustion. A catalytic afterburner at 300 to 400 degrees Celsius or a thermal oxidiser at 700 to 800 degrees Celsius destroys 95 to 99 percent of the VOC load. Boutique roasters under 5 kg batch size often qualify for exemptions; larger machines in mixed-use precincts almost always need secondary combustion.

What is the difference between 304 and 316L stainless for food manufacturing duct?

Both are austenitic stainless steels suitable for food contact. 316L adds 2 to 3 percent molybdenum which improves resistance to chloride pitting and acidic condensate. For general food zone, packaging halls and dry storage, 304 is the cost-effective choice. For chocolate conching and tempering, sugar panning and caramel cooking, and any zone with heavy CIP chloride exposure, 316L is mandatory. EHEDG Doc 8 recommends 316L for all direct product-contact and product-splash zones.