UL 300 Explained: The Test Standard for Restaurant Fire Suppression Systems

Why UL 300 was created

Older dry-chemical kitchen systems worked by reacting with animal fat (lard) to form a soapy blanket on the burning oil, a process called saponification. Kitchens moved to vegetable oils, which have less saturated fat and a higher autoignition temperature, and to well-insulated high-efficiency fryers that hold heat longer. Those fires burn hotter and cool more slowly, so the soap blanket breaks down and the oil can reignite.

What UL 300 changed in testing

According to the Fire Equipment Manufacturers’ Association (FEMA), UL 300 introduced these major test changes:

• A real commercial gas fryer with specified heating and cooling rates replaced a fabricated pan.
• The preburn after autoignition went from one minute to two minutes.
• The appliance stays fuel-on during preburn instead of being shut off.
• A minimum grease autoignition temperature of 685°F (363°C) was added.

Dry chemical vs wet chemical

All previously listed restaurant systems had to be retested to UL 300. Dry-chemical systems did not meet the new requirements: they could knock the fire down but reflash was likely because they did not cool the oil enough. Wet-chemical systems were modified to pass. That is why essentially every new kitchen hood system installed today is wet chemical.

Is a pre-UL 300 system still allowed?

It depends on your local authority having jurisdiction (AHJ), your insurer, and the system’s condition. FEMA recommends upgrading a pre-UL 300 system to a UL 300 system when any of the following apply:

• Cooking appliances, hoods, or ducts in the protected area change, appliances are added, or the kitchen switches to vegetable-based oils.
• The system manufacturer or another fire protection expert recommends an upgrade.
• The local fire authority, insurance company, or another authority requires or recommends it.
• Parts or agent are no longer available to service the existing system (noted by EMC Insurance).

How to tell if your system is UL 300 listed

• Read the nameplate on the agent cylinder and the control head for the brand and model (for example Ansul R-102 or Piranha, Kidde WHDR, Amerex KP, Pyro-Chem Kitchen Knight II).
• Check the last inspection report, which usually names the system model.
• Ask your inspector. A licensed, factory-trained technician can confirm the listing and whether the current appliance layout is still within it.