Restaurant Deep-Fryer Fire and Suppression Performance
A restaurant kitchen fire at 18:45 started in a 40 L deep fryer and extended into the exhaust hood and duct. The hood suppression system discharged, but the fire continued. The fryer had a thermostat set to 350°F; the oil level was below the minimum mark. The fryer was manufactured in 2015 and the thermostat had been replaced twice. The suppression system had been inspected 8 months earlier; the fusible link above the fryer was rated 360°F and was installed 18 inches above the fryer. The duct had no access panel and had not been cleaned in 2 years. The investigator must determine origin and cause and whether the suppression system failed. NFPA 1033 requires examining fuel gas systems, appliances, and suppression systems.
1. What is the likely origin and cause, and what evidence supports it?
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The origin is the deep fryer, with extension into the hood and duct. The low oil level below the minimum mark and the thermostat set to 350°F support overheating of the oil. The fusible link rated 360°F installed 18 inches above the fryer may have been too high or too far from the cooking surface to actuate promptly, but that is a hypothesis to test against the manufacturer's listing. The suppression system discharged, yet the fire continued, which could be due to the fire being in the duct above the hood, a blocked nozzle, or insufficient agent. The investigator should test the fryer thermostat and high-limit control, examine the oil level and fryer controls, and verify the suppression system's design, inspection, and discharge. NFPA 1033 requires examining appliances and suppression systems. The cause should not be attributed to the suppression system without evidence that it failed to perform as designed.
2. How should the investigator evaluate the suppression system's performance?
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The investigator should document the hood, plenum, duct, and fryer configuration; record the nozzle locations, piping, and agent cylinder pressure; and verify the fusible link rating, placement, and orientation against the listing. They should interview employees about the discharge, the manual pull station, and whether the system had been serviced. Maintenance records from 8 months earlier should be reviewed for deficiencies. The investigator should test the system components if safe and compare the discharge pattern with the fire damage. If the fire was in the duct, the hood suppression system may not have been designed to extinguish it. NFPA 1033 requires a systematic examination. The conclusion should distinguish between a system failure, a design limitation, and an improperly maintained system.
3. What documentation is needed for the duct fire and the lack of an access panel?
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The investigator should photograph the entire duct run, the hood, the fan, and any grease accumulation; measure the grease depth and record the duct material and size. The lack of an access panel and the 2-year cleaning interval are code and maintenance issues that should be documented with the applicable standards. The investigator should obtain the cleaning records, the suppression inspection report, and the restaurant's fire safety plan. Samples of duct grease may be collected for laboratory analysis. NFPA 1033 requires documentation and evidence collection. The report should explain how the duct condition affected fire spread and suppression, but it should not use the code violation as proof of cause. The origin remains the fryer; the duct condition is a contributing factor to extension.