Propane Leak on the Night Shift
At 02:10, Officer Patel is on foot patrol at a metal-fabrication plant with 38 workers on the night shift. Near the propane tank farm, he smells a strong mercaptan odor and hears a steady hissing from a tank connection. Frost is visible on the valve. The wind is blowing toward the loading dock, where six workers are wrapping pallets. The plant's gas detection system has not alarmed, and the shift supervisor does not answer the radio after two attempts. Patel has a two-way radio, a cell phone, a flashlight, and no gas monitor or respirator. The tank farm is 30 feet from the maintenance shop, where a forklift is running. A contractor's truck is parked within 20 feet with its engine idling. The plant's emergency action plan is posted in the guardhouse, 200 yards away.
1. List Patel's immediate priorities and the order in which he should act.
Read the worked answer
Life safety comes first; stopping the leak is not Patel's job and he is not equipped for it.
- Move away and upwind. Do not approach the hissing connection or try to close the valve without training, PPE, and a gas monitor. Put distance and wind direction between himself and the tank farm.
- Alert and evacuate. From a safe upwind location, radio the plant emergency channel and tell workers to evacuate the loading dock and maintenance shop. If the plant has a manual alarm or public-address system, activate it from a safe location. Tell people not to run through the vapor cloud and not to start vehicles.
- Call 911. Give the address, the product (propane), the location of the leak, the hissing and frost, the wind direction, the number of workers, and any injuries. Ask for the fire department and utility or plant emergency coordinator.
- Notify the chain of command. Keep trying the shift supervisor and call the plant emergency contact listed in the plan.
- Establish a safe perimeter and account for personnel at the designated muster point, keeping people upwind and out of the vapor path.
2. What ignition sources and exposure risks must be controlled, and what should Patel not do?
Read the worked answer
Propane vapor is heavier than air, can travel along the ground, and can ignite far from the leak. The running forklift and the idling contractor truck are immediate ignition risks. They should be shut down only if a worker can do so without entering the vapor area or creating a spark; otherwise keep everyone away and let the fire department handle equipment in the hazard zone.
Patel should not:
- Operate electrical switches, vehicle ignitions, or equipment in or near the vapor area.
- Use the flashlight or radio inside the vapor cloud unless the equipment is rated for a flammable atmosphere. Use them from a safe upwind distance.
- Attempt to close the valve, plug the leak, or move the propane tanks.
- Re-enter to look for people without accounting for them at the muster point and without fire department direction.
- Assume the absence of an alarm means there is no leak. The odor, hissing, and frost are positive indicators.
He should also keep spectators and traffic out of the area and prevent anyone from smoking or using a phone near the perimeter.
3. What should happen before re-entry, and what should Patel document?
Read the worked answer
No one should re-enter the hazard area until the fire department or a qualified plant emergency coordinator declares it safe. Re-entry should be based on atmospheric monitoring and control of the leak, not on the odor fading. The fire department should confirm the perimeter, isolation distance, and whether nearby equipment can be restarted safely.
Patel should document:
- The exact time he first noticed the odor, the hissing, and the frost.
- His location and the wind direction at the time.
- The time of each radio attempt, the 911 call, the evacuation order, and the supervisor notification.
- Which workers were evacuated from the loading dock and maintenance shop, and the muster count.
- The equipment running near the tanks, including the forklift and contractor truck.
- Any injuries, complaints, or people who refused to leave.
The report should separate what he directly observed from what others told him. He should also note that the gas detection system had not alarmed, because that is a safety-system failure worth investigating.