Container Restaurant Exhaust Hood Makeup Air Ontario

By Paul LeBlanc, owner, and Christian LeBlanc, second-generation operator, Van Blanc Ent. Inc.

Reading time: about 14 minutes.

Type 1 or Type 2: Which Hood Does My Cookline Require?

A container restaurant hood is either Type 1 or Type 2, and the cookline decides which. A Type 1 hood is required over any appliance that produces grease-laden vapour or smoke: fryers, charbroilers, griddles, woks, ranges. A Type 2 hood covers heat and moisture only, from steamers and clean-burning ovens. Most container restaurants run Type 1.

The first decision in a container restaurant build is not the hood model. It is the cookline. NFPA 96 keys the entire ventilation package to whether the equipment under the canopy produces grease-laden vapour, condensate, smoke, or just heat. Fryers, charbroilers, griddles, woks, salamanders, ranges, and even a busy panini press push you straight into Type 1 territory. Steamers, dishwashers, and pizza ovens that burn clean often live under Type 2.

Most container restaurants in Ontario lean toward Type 1 by default because the menu drives the build. Burgers, smash patties, fried chicken, fish and chips, shawarma, taco al pastor on a vertical broiler, ramen with wok heat, brisket on a flat-top: all of it produces grease vapour that has to be captured, condensed, and exhausted through a fire-rated duct chase.

The reason this matters at the very start is that a Type 1 system pulls more air, requires more makeup air, needs a fire suppression system, demands a UL 1046 grease-filter bank, and triggers a clearance-to-combustibles review around your container’s interior wall framing. A Type 2 install is lighter on all four counts. Most operators do not appreciate the gap until the first plan-check comment arrives. Settle the hood class on day one and the rest of the design slots into place.

What Does an NFPA 96 System Look Like Inside a 20ft Galley?

An NFPA 96 system inside a 20ft galley is a single chain of five linked parts: hood capture, grease-bank filtration, fire-rated welded duct, a curb-mounted upblast fan on the roof, and wet-chemical suppression in the canopy. A working container restaurant runs all five as one chain. Capture happens at the hood. Filtration happens at the grease bank inside the canopy. Conveyance happens through a fire-rated welded duct (16-gauge carbon steel or 18-gauge stainless minimum per §7.5) that rises through the container roof to a curb-mounted upblast fan. Suppression sits inside the canopy as a wet-chemical pre-engineered system tied to fusible links and the fuel shutoff. Cleaning schedules under Table 11.4 dictate how often the bank, duct, and fan get scraped, depending on cooking volume.

The discipline of fitting all of that into a 20ft (6.06m) or 40ft HC (12.19m × 2.9m interior height) shipping container is what separates a restaurant build from the lighter office and workshop builds we turn out of the yard. You are working inside the 7’9″ interior width of a standard dry container, or roughly 8’10” interior height on a high cube. The roof becomes structural for the curb. The walls become combustible-clearance surfaces around the duct chase. The floor takes the weight of the gas equipment plus the makeup-air handler if it is mounted inside. Every centimetre is engineered.

Buyers comparing options usually arrive with one of three rough mental pictures: a food-truck cookline shoved into a steel box, a backyard kitchen scaled up, or a real commissary kitchen scaled down. The last one is the right reference. A container restaurant is a small fixed commissary that lives outdoors. NFPA 96 does not bend because the building has corner castings. Apply it the same way you would in a strip-mall hot food unit, and the inspection goes clean.

How Much Exhaust CFM Does a Container Cookline Need?

Exhaust CFM for a container cookline is engineered from the equipment under the hood, not guessed from the container size. As a working band, a 4-foot hood over a six-burner range and a fryer runs 1,200 to 1,600 CFM; a 6-foot hood over a charbroiler and salamander climbs to 2,000-2,400 CFM. NFPA 96 sets minimum exhaust flow per linear foot of hood, but the practical number depends on the equipment underneath. Step up to a 12-foot island canopy over a wok line and a charcoal grill and you can hit 6,000 CFM. The number is engineered, not guessed.

The container length sets the upper bound. A 20ft galley can accommodate roughly a 4-6 foot cookline once you account for the prep counter, sink wells, refrigeration, the customer service window, and circulation. A 40ft HC allows an 8-10 foot cookline plus all of that. The hood length tracks the cookline plus a 6-inch overhang each side per NFPA 96 §5.1.2, with a mounting height of 78-84 inches off the finished floor to clear the chef and still capture the plume.

The CFM band moves with appliance heat output. A charbroiler runs hotter than a griddle, which runs hotter than a six-burner. Mechanical engineers apply NFPA 96 Annex B factors that adjust the per-foot rate by appliance duty. The capture rule never bends, but the resulting exhaust number changes by 25-40% across cookline types of the same length. Get your engineer the actual menu and equipment cut sheets, not a generic appliance count.

Why Size Makeup Air at 80% of Exhaust?

Makeup air in a container restaurant is sized at 80% of exhaust CFM so the galley holds a slight negative pressure: the fan pulls more air out than the unit pushes back in, and the small remainder infiltrates through the service window and door cycles. That slight negative is what pulls the cookline plume up into the hood instead of letting it drift past the filters. Exhaust air does not just leave. Whatever volume the upblast fan pulls out the roof has to come back in through a deliberate path. In conventional buildings, code lets the building’s HVAC supply the difference. Inside a sealed container restaurant, there is no building HVAC bleeding in across thirty windows. The makeup air is engineered or the kitchen does not work.

The industry standard is to size the dedicated makeup-air unit (MUA) at 80% of exhaust CFM. The remaining 20% is allowed to infiltrate through the service window, door cycles, and intentional transfer grilles. This keeps the kitchen at slight negative pressure relative to outside, which prevents smoke and odour from rolling backward through the dining counter. Push the ratio past 90% and the room goes neutral or positive, which causes capture failure at the hood: grease vapour drifts past the filter bank and condenses on the ceiling.

The MUA itself can be gas-fired, electric, or indirect-fired depending on the climate strategy. Ontario operators almost always specify a gas-fired direct-fired heater on the MUA because the winter design temperature in Brantford, Hamilton, and the GTA can drop below -25°C and the supply air still needs to land in the room at around 18-21°C. An undersized or untempered MUA throws -10°C air at the cook’s back through January, and the kitchen empties out before the lunch rush is over. Tempered makeup air is not optional in this climate.

How Does the Exhaust Fan Mount on a Container Roof?

The exhaust fan mounts on a welded steel curb that sits on top of the container roof, never directly on the corrugated steel. The curb spreads the fan weight, vibration, and duct load onto the long roof rails or a flat-bar perimeter, and the upblast fan bolts to it on a hinged base for cleaning access. The container roof is the structural slab in this conversation. ISO 6346 dry containers have a corrugated steel roof rated for a stacking load when full of cargo, but the roof was never engineered to carry a 200-pound upblast fan with vibration cycles, a four-foot duct stub, and a curb that captures rain and drains to the roof gutter line. The structural review starts there.

The standard pattern: a welded steel curb sits on top of the existing container roof, with the corrugation flattened or bridged by gusset plates underneath. The curb is welded to the roof rails or to a flat-bar perimeter that distributes the load to the long sides. The duct chase rises through the curb opening, lined with fire-rated insulation per NFPA 96 §7.6 clearance-to-combustibles, and the upblast fan bolts to the curb with a hinged base for cleaning access. The result is a properly tied roof penetration that drains away from the duct and holds in 90 km/h gusts.

Why Does My Container Kitchen Door Slam or Stick?

A container kitchen door that slams shut or sticks is telling you the exhaust and makeup air are out of balance. When the two airflows are off by more than 100-200 CFM, the pressure differential across the small steel envelope overwhelms the door hardware. A container restaurant tells you fast when the pressure is wrong. The service window will not close cleanly. The walk-in cooler door creaks when the kitchen exhaust ramps up. The customer counter door slams in your face or sucks shut and traps your hand. These are not nuisance items. They are diagnostic signals that the exhaust and makeup-air are not balanced.

The math is simple. Exhaust pulls air out. Makeup air pushes air in. Doors, windows, transfer grilles, and infiltration paths handle the small remainder. When the math is off by more than 100-200 CFM in either direction, the pressure differential is large enough to overwhelm the door hardware. Slight negative is the target. Strong negative starves the burners and pulls the pilot flame off the manifold. Positive pushes smoke and grease backward into the customer area.

The fix is almost always at the MUA controller. Variable-speed MUA units track the exhaust fan signal and ramp together: when the hood fires, both fans start; when the cook line drops to idle, both fans throttle. The interlock is what produces the slight-negative target across changing cooking loads, not a fixed-speed fan running at one CFM all day.

Does Makeup Air Need Heating for an Ontario Winter?

Makeup air for an Ontario container kitchen has to be tempered, because pulling raw winter air across the cookline makes the room unworkable. The 2.5% winter design temperature for Brantford is around -19°C, and supply air still has to land in the room near 21°C. The Ontario climate is the engineering constraint that most American container-kitchen plans get wrong. Hamilton and Toronto sit at similar winter numbers. Sudbury drops to -33°C. Pulling 2,000 CFM of outdoor air at -19°C into a cookline at 21°C without tempering means dropping a continuous 40°C delta across the cook’s shoulders. The kitchen becomes unworkable inside ten minutes and the food quality suffers because the cook is fighting the climate, not the burner.

Direct-fired gas MUA units are the default in Ontario commercial kitchens because they hit 92% thermal efficiency and produce supply air at the room set point with very little energy lost to flue. The burner sits in the airstream, the products of combustion are diluted, and the air arrives at 18-21°C even when the outside reads -25°C. Indirect-fired units cost more, lose efficiency to the flue, and are only specified when there is a regulatory concern about combustion products inside the kitchen, which most jurisdictions resolve via direct-fired heater listings under ANSI Z83.4 / CSA 3.7.

What Fire Suppression Does a Container Cookline Need?

A container cookline running a Type 1 hood needs a wet-chemical pre-engineered fire suppression system listed to UL 300, installed under NFPA 17A and 96. The agent saponifies hot grease on contact, the nozzles fire when fusible links melt or the manual pull is hit, and the same trip shuts off the gas and kills the cookline circuits. Type 1 hoods over grease equipment in Ontario require this system as standard. The potassium-based agent smothers the fire and cools the cookline, the fusible links inside the hood plenum melt at 360°F, and the trip closes a mechanical gas valve and cuts power to every cookline circuit at once.

Inside a container, the clearance-to-combustibles review around the duct chase and the hood penetration is the part that catches first-time operators. The container’s interior wall framing, if it is wood or any fibre-board sheathing, must be replaced or shielded with non-combustible sheet at the duct chase. NFPA 96 §7.6 calls for 18 inches of air gap or a listed thermal barrier. The fire suppression system extends only to the hood and the protected cookline; the chase clearance is a separate envelope-protection requirement.

What Mechanical and Electrical Sign-Offs Does the Build Need?

An Ontario container restaurant clears the same mechanical and electrical sign-offs as any food-service occupancy: a mechanical review of the hood, duct, MUA, and gas line, an Electrical Safety Authority review of the cookline circuits and suppression interlock, a fire department review of the suppression system, and public health for food handling. An Ontario container restaurant runs the same gauntlet as a strip-mall hot-food unit, with the structural roof modification reviewed alongside the mechanical package. Each sign-off is an independent inspector with their own checklist, so the build either coordinates them up front or trips over them one at a time.

The path that works: produce one set of coordinated drawings that show the cookline, the hood, the duct routing, the MUA placement, the roof curb detail, the gas line schematic, the electrical riser, and the suppression layout on shared sheets. Submit them as a single mechanical package with the building permit. Inspectors prefer one document set over five disconnected ones. Operators who try to permit each trade separately almost always hit a coordination comment that sends them back to the drafting table.

What Does Van Blanc Spec for a Container Cookline?

Van Blanc specs a container cookline as a sequence, not a parts list: start with the menu, pick the cookline, size the hood, calculate exhaust CFM, set the makeup air at 80% tempered and gas-fired, engineer the roof curb, weld the duct, add UL 300 suppression, interlock the fans and shutoffs, and bond the shell. Each step carries a detail worth pinning down: the hood runs cookline length plus 6 inches each side, the exhaust CFM comes from NFPA 96 Annex B factors against the real equipment list, the MUA lands gas-fired and tempered to 18°C, the duct is welded 16-gauge carbon or 18-gauge stainless in an insulated chase, and the roof curb distributes the fan load onto the long roof rails. The order matters as much as the parts. Skip ahead to the curb before the cookline is locked and you reweld it later.

The same logic threads through every food-service box we ship, starting with the overview of what a container kitchen build involves end to end for new operators. The ventilation package sits alongside the wastewater side of the same cookline, so it pays to read how a grease interceptor gets sized and plumbed into the galley at the same time you spec the hood. Buyers who reach this page are usually deep enough into the project to be ordering long-lead items, where the exhaust and MUA start to bite the schedule. Order both with at least eight weeks of lead time on a winter delivery. The fit-out details, from venting to roll-up doors, live on our yard conversion and modification program.

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