Odor Call at a Restaurant with 25% LEL Near the Range
At 02:15 a restaurant manager calls the gas utility reporting a strong gas odor in the kitchen and dining room. A two-person crew arrives. They smell mercaptan at the front door, see 14 customers and staff in the parking lot, and learn that an employee shut off the lights and the range but did not shut off the gas main. A combustible gas indicator reads 10% LEL at the door and 25% LEL near the kitchen range. The building has a basement, a rooftop makeup-air unit, and a 2-inch gas service with an outside meter/regulator set. The crew has a four-gas monitor, leak-detection fluid, and hand tools. Ambient temperature is 2°C, and the air is calm.
1. List the crew's immediate priorities and actions on arrival.
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Priorities: protect life, prevent ignition, isolate gas, ventilate, then find the leak. The crew should not enter the building at 25% LEL without appropriate PPE and continuous monitoring; they should call the fire department, establish a hot zone, and keep people away. Shut off the gas at the outside meter/regulator service valve, not at an appliance. Do not operate light switches, doorbells, cell phones inside, or the rooftop unit. The employee who turned off lights and the range may have created a spark risk; treat the building as energized until gas is isolated and ventilated.
2. Interpret the 25% LEL reading and explain the entry and ventilation decisions.
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25% LEL is above the common 20% LEL emergency action level. Natural gas LEL is about 5% by volume, so 25% LEL is roughly 1.25% gas in air-well into the flammable range if a source ignites. The 10% LEL at the door shows the plume has spread. Ventilate from outside using explosion-proof equipment or natural ventilation after shutting the gas, and re-enter only with a CGI and a second person. The basement is a particular concern because gas and vapors can accumulate there; monitor the basement stairwell before anyone descends. Do not use the four-gas monitor as a substitute for a calibrated CGI if it is not set up for %LEL.
3. Describe the leak-location, repair, and reoccupancy steps.
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After isolation and ventilation, use leak-detection fluid on the range connector, manifold, shutoff, and any union; also check the meter/regulator set and service riser. A 25% LEL near the range suggests an appliance connector or valve leak, but the basement and service must be ruled out. Repair or replace the defective component, then pressure-test the repaired section per the utility's procedure, purge, and relight only after the manufacturer's instructions are followed. Reoccupancy criteria: 0% LEL, no gas odor, a successful leak test, and confirmation that the appliance is operating correctly. Document the readings and notify the fire department before reoccupancy.