Fires are a major threat to restaurants. If not deadly, they are costly and possibly business ending. According to a study by the National Fire Protection Association (NFPA), between 2010 and 2014, sixty-one percent of restaurant fires involved cooking equipment1. Per Buda-Ortins, approximately two-thirds of cooking fires begin with the ignition of cooking oils2. Thus, it’s important to protect a restaurant against the hazards of combustible cooking media (animal fats and vegetable oils).
Cooking oils require unique safeguards as they are combustible and produce ignitable vapors once heated. Commercial kitchens use the following equipment to increase occupant safety:
- Exhaust systems,
- Automatic fire suppression systems,
- Wet chemical fire extinguishers, and
- Containers for grease-laden linens.
Commercial cooking appliances, used in processes producing grease-laden vapors, are equipped with exhaust systems that comply with the Standard for Ventilation Control and Fire Protection of Cooking Operations (NFPA 96). These systems include a hood, grease filter, and exhaust ductwork. It’s important that the system incorporates the following properties:
- A well deigned airflow,
- Clearances to combustibles,
- Liquid tight, stainless steel construction,
- Grease removal devices, and
- An automatic suppression system.
The automatic suppression system is designed to protect the hood exhaust plenums, grease removal devices, and exhaust duct systems. This is accomplished by aiming nozzles at individual cooking appliances. Thus, it’s important to update the system when rearranging or introducing new equipment. Fires can spread by moving appliances from their original layout, resulting in a mismatch of nozzles and equipment. The suppression system is activated manually or automatically by thermal links. Good housekeeping is important to keep the system in proper working order. Systems can fail if their thermal links are coated with hardened grease3.
NFPA 96 requires hoods to be inspected and tested by properly trained, qualified, and certified persons every six months. The standard also details hood and duct cleaning frequencies based on a restaurant’s cooking volume, as catalogued in Table 1.
Table 1: Schedule of Inspection for Grease Buildup4.
|Type or Volume of Cooking||Inspection Frequency|
|Solid fuel cooking operations||Monthly|
|High-volume cooking operations†||Quarterly|
|Moderate-volume cooking operations||Semiannually|
|Low-volume cooking operations‡||Annually|
† High-volume cooking operations include 24-hour cooking, charbroiling, and wok cooking.
‡ Low-volume cooking operations include churches, day camps, seasonal businesses, and senior centers.
The Standard for Portable Fire Extinguishers (NFPA 10) regulates the selection, inspection, maintenance, recharging, and testing of fire extinguishers. It requires most facilities be equipped with ABC type fire extinguishers. These are dry chemical extinguishers that extinguish most fires; Class A for trash, Class B for liquids, and Class C for energized electrical sources. However, ABC type fire extinguishers are not designed to extinguish combustible cooking media. Thus, Class K extinguishers are required to be present wherever cooking oils are used. These are wet chemical extinguishers that extinguish grease fires by saponification.
Oily linens can spontaneously combust. Oil oxidizes in air, which produces heat. Higher temperatures lead to increased oxidation, which creates more heat. In a pile of oily linens, heat is unable to dissipate, and the combustible material is heated to its autoignition temperature. Thus, it’s important to store and dispose dirty linen in containers with tight fitting lids. This limits the amount of oxygen supplied to the oily residue and thus limits oxidation of the oil. Even after laundering, linens have the potential to self-heat and ignite. According to the Soap and Detergent Association (SDA), linens can spontaneously combust while containing only three percent oil residue5. Thus, clean linens are also stored in containers with tight fitting lids.
In closing, fires are a major threat to restaurants. If not deadly, they are costly and possibly business ending. As most restaurant fires involve cooking equipment, it’s important to understand the hazards associated with combustible cooking media. By identifying and preventing such hazards, one reduces the risk of fire.
Written By: Mark Richards, PE
1 Campbell, Richard. Structure Fires in Eating and Drinking Establishments. Quincy, MA.: National Fire Protection Association, 2017.
2 Buda-Ortins, Krystyna. Auto-Ignition of Cooking Oils. College Park, MD: University of Maryland, 2010.
3 Horton, Doug. “Lessons Learned from Commercial Kitchen Fire Investigations.” ASHRAE Journal February 2015.: 18-26.
4 Standard for Ventilation Control and Fire Protection of Cooking Operations (NFPA 96-2017). Table 11.4. Print.
5 Soap and Detergent Association memo and report titled “Removal of Cooking Oil from Cotton Terrycloth Towels” https://www.cpsc.gov/s3fs-public/os3.pdf