Kitchen hood suppression systems: the hazard, the system and the inspection

A kitchen hood suppression system is the hood, the listed system that discharges on a fire, and the shutdowns that stop the appliances feeding it. NFPA 96 covers the hood and exhaust side, and NFPA 17A the extinguishing system.

What triggers the requirement

Commercial cooking equipment that produces grease laden vapors gets a hood, and that hood gets a listed suppression system (NFPA 96 Chapters 1 and 10). The grease decides it, not the size of the kitchen.

When an existing system has to be brought up to date

Automatic extinguishing systems meet UL 300 or an equivalent standard (NFPA 96 Chapter 10, NFPA 17A). An existing dry or wet chemical system that does not meet it has to be brought into compliance when any one of four things happens:

• The cooking medium changes from animal oils and fats to vegetable oils.
• The positioning of the cooking equipment changes.
• Cooking equipment is replaced.
• The equipment is no longer supported by the manufacturer.

Any change to the hazard after installation also means the design is re-evaluated by a trained, qualified and certified person. Baffle plates or shelves that block the nozzle spray pattern are not allowed at all, and abandoned pipe or conduit from an old system comes out of the hood, plenum and duct, with the holes sealed liquidtight.

What happens when it discharges

The fan and makeup air rules share one exception: fan shutdown required by a listed component of the ventilation system, or by the design or listing of the extinguishing system (NFPA 96 Chapter 10). It is makeup air supplied inside the hood that shuts off, not every source of replacement air.

The manual pull

The manual pull sits along the way out of the cooking area, at a reachable height, and far enough from the appliances that somebody can still get to it during a fire (NFPA 96 Chapter 10, NFPA 17A). A pull mounted behind the fryer line is unusable at the moment it matters. Walk the egress path and see whether you would actually reach it.

Inspection, filters and cleaning

The system is inspected and serviced on a set interval by a qualified person, and the record stays on site (NFPA 96 Chapter 11, NFPA 17A Chapter 7).

Grease filters are listed, noncombustible, sturdy enough not to distort in use or cleaning, easily removable, arranged so all exhaust air passes through them, and set at least 45 degrees from horizontal over a drip tray that drains to an enclosed metal container of no more than 1 gallon (NFPA 96 Chapter 6). Look for gaps at the ends of the filter bank. Mesh filters are not banned outright: they are allowed as part of a listed hood or when listed with a primary filter.

How often the hood, duct and exhaust are cleaned follows how hard the kitchen works, not the calendar alone (NFPA 96 Chapter 11). A wood fired pizza oven on an annual clean is four cleanings short.

Coordinate the trades and check the licenses

Where the hood system is connected to the building fire alarm, kitchen suppression work and fire alarm work meet at the same point. If the kitchen contractor and the fire alarm contractor are different companies, coordinate with the fire alarm vendor before working on the hood system, so the fire alarm side knows it is being worked on, and test the connection between the two together.

Licensing is often separate for each trade. Depending on the state and the jurisdiction, kitchen suppression, fire alarm and electrical work can each need their own license, and the work on a specific system can call for training and certification on that system. Make sure whoever does each part of the job is properly licensed, trained and certified for it.