Aug 2013

Kitchen Hood Suppression Systems

You may have a wet or dry chemical system in the hoods above cooking equipment in your kitchen. Both of these systems should be tested at least semi-annually by a service technician per NFPA 17A, Wet Chemical Extinguishing Systems, and NFPA 17, Dry Chemical Extinguishing Systems. Additionally, monthly owner’s inspections shall also be conducted in accordance with the owner’s manual for the system. This includes, but is not limited to: ensuring that the system has not been tampered with; having the last inspection tag in place; ensuring that pressure gauge(s), if provided, are in the operable range; nozzle blowoff caps being in place and undamaged; ensuring that no obstructions are present; and determining that the hazard has not changed.

Deep fat fryers have become better insulated, and many kitchens have switched from animal fat to lower-fat vegetable oils with higher auto-ignition temperatures. The problem with the higher auto-ignition temperature is that these fires burn hotter, so they are more difficult to extinguish and the fire could re-ignite spontaneously. The well insulated fryers also help to keep the temperature above the auto-ignition temperature, which results in a longer lasting fire.

Fire-extinguishing systems for use in cooking operations shall comply with ANSI/UL 300, Fire Testing of Fire Extinguishing Systems for Protection of Commercial Cooking equipment. This is a fire testing standard administered by Underwriters Laboratories (UL). This standard was published in November 21, 1994. It was about this time that better insulated fryers were being used and when the switch was made to vegetable oils in many kitchens.

The UL 300 standard specifies testing procedures to protect a range of equipment, such as fryers, range tops, griddles and char-broilers. The UL 300 tests better simulate actual conditions than previous test methods.

For example, the suppression test for a fryer used to allow a mocked-up fryer. However, the new test requires that an actual fryer be used and specifies heat-up and cool down rates. Additionally, the new test requires oil with an auto-ignition temperature that better matches that of vegetable oil. This test also factors in: the potential for the heating element to stay on and a 2 min. burn before suppression system activation. Splashing of flaming cooking oil outside of the fryer is not allowed and the foam blanket must secure the fire for at least 20 minutes.

When this standard was released, manufacturers had to retest their existing systems to verify compliance with the UL 300 guidelines. None of the dry chemical systems have been able to meet these requirements, as they can smother the fire but do not provide cooling. Wet systems have proven more effective, since they also provide cooling. However, many of the existing wet systems had to be upgraded with increased flow rates, more flow nozzles and an increase in agent capacity to meet these requirements.

Retrofitting an existing non-compliant system may or may not be possible. If it is possible to upgrade such a system, then this must be done in accordance with the manufacturer’s UL Listing. One such upgradable system, the Ansul R-102 system, will be discussed here. All UL 300 R-102 surface protection requires pressure to be regulated from a piston-style regulator that nominally supplies 110 psi to the agent storage tanks. The diaphragm-style regulator was factory set at a nominal 100 psi. Hood and duct protection did not need to be retested in 1994. Thus, either style of regulator may be used in these systems.

The Ansul R-120 systems manufactured after November 21, 1994 are in accordance with the UL 300 standard. The R-102 systems manufactured from November 1989 to November 1994 used a piston style regulator, so the only upgrades needed are using UL 300 nozzles. The R-102 assemblies manufactured from 1982 to November 1994 also would need the diaphragm-style regulators changed to UL 300 Regulated Actuator Assemblies – that are a piston-style regulator. The remaining components of these systems can typically be retained.

Please note that pre- UL 300 systems that were removed from service should not be reinstalled. Systems that are modified should also be upgraded. NFPA is allowing the Authority Having Jurisdiction (AHJ) and the insurance companies to decide if the older systems must be upgraded or not on systems that have not been modified.

If you have questions regarding the testing of your suppression system or whether system upgrades are needed or not, please feel free to contact Risk Logic for assistance.