How a Dirty Hood and Duct System Becomes a Restaurant Fire Hazard

A dirty hood system causes restaurant grease fires because condensed cooking grease is fuel sitting directly above an open flame. Vapour rises off the line, cools on the filters, plenum walls and duct interior, and hardens into a varnish-like layer. A flare-up from a charbroiler or a fryer that boils over sends flame into the hood, and that flame meets a fuel surface that runs the entire length of the duct. Most cooking oils auto-ignite somewhere around 315-370°C - well inside the range a grease flare-up reaches.

Why the duct is the dangerous part, not the hood

Filters catch some grease, but they are only the first stage. What passes through condenses in the plenum behind them, then in the horizontal duct run, then in the vertical riser to the rooftop fan. Once burning, a grease duct fire behaves differently from a stovetop fire: it spreads fast along a confined fuel path, it is largely out of reach of a hand extinguisher, and it travels through the ceiling cavity to wherever the duct goes. In older Red Deer and Lacombe strip-mall buildings with long horizontal runs above a shared demising wall, that can mean the neighbouring tenant's space.

What Alberta requires

The Alberta Fire Code (Division B, Section 2.6) requires that commercial cooking exhaust equipment be maintained so grease does not accumulate, and it adopts NFPA 96 as the standard of practice. NFPA 96 Chapter 11 sets inspection frequency by cooking volume - roughly monthly for solid fuel, quarterly for high-volume operations, semi-annually for most sit-down restaurants, annually for low-volume kitchens - and requires cleaning to bare metal, not just filter swaps. Your local fire authority is the AHJ and can order correction. See how often NFPA 96 says your kitchen needs cleaning.

How an insurance adjuster reads the scene

After a commercial kitchen fire, the adjuster and origin-and-cause investigator look at the duct interior, the filter condition, and your paperwork. Missing or overdue cleaning certificates, filters left out, an access panel never opened, or a fan that was never lifted are all documented. A policy that carries a hood-cleaning maintenance warranty can be contested when there is no record. NFPA 96 compliance protects two things: the building, and the owner's position afterward. The certificate and dated service sticker are the evidence.

Costs and getting it looked at

In Central Alberta, most single-hood restaurant cleanings run roughly $350-$700; multi-hood kitchens with long vertical risers and rooftop fans more often run $900-$2,000. Solid-fuel and wood-fired setups sit higher because of frequency.

This site is an independent referral service - we are not the cleaner. Calls go to one vetted hood cleaning contractor working Red Deer and the surrounding Central Alberta towns, who will inspect the full duct run and issue NFPA 96 documentation. If you are unsure what a full clean should include, read what a proper hood cleaning covers.