What Does Commercial Kitchen Hood Suppression Design Require?

Commercial kitchen hood suppression requires a listed wet-chemical system with nozzles in the hood and duct, plus coordinated exhaust, grease-tight ductwork, makeup air, and automatic gas shutoff. The design must tie into the building fire alarm and pass the fire marshal's inspection of the whole cooking operation — not just the suppression nozzles. What I've learned from restaurant projects is that the suppression system is the easy part to buy and the hard part to coordinate. Four trades touch the cooking line, and the fire protection only works when all four did their jobs. The engineer who owns the coordination owns the outcome.

Start with the cooking equipment — the actual appliances define everything downstream. The hood is sized and listed for that equipment line, with the right overhang and exhaust rate to capture the thermal plume. The duct from the hood to the outside is grease-tight welded construction with cleanouts at every change of direction, because grease accumulates and grease burns. The suppression system lives inside that duct and hood: detection (fusible links rated for the temperature above each appliance) and nozzles aimed at the hazard zones — the cooking surfaces, the plenum, the duct. On activation, the system discharges wet chemical that saponifies the burning grease, shuts the gas, signals the building fire alarm, and controls the fans per the sequence. Makeup air is the forgotten piece: the exhaust pulls hundreds or thousands of CFM out of the kitchen, and if replacement air isn't provided, the space goes so negative that doors slam, pilots blow out, and the hood can't capture properly.

Fire marshals inspect cooking operations as a system, and they find the gaps between trades. Here's what I make sure is covered before they walk in. My kitchen fire protection checklist.

• Listed suppression matched to equipment: nozzle layout verified against the actual appliance lineup, not the original plan
• Fuel shutoff interlocked: gas valve closes on activation, tested — not just drawn on the plans
• Grease duct detailed: welded, grease-tight, with cleanouts, and a cleaning contract in place
• Makeup air provided: exhaust CFM balanced so the kitchen and dining room pressurization works
• Alarm interface complete: suppression activation reports to the building fire alarm panel