Handling Gas Leak Emergencies An Update

On Dec. 27, 1983, our nation suffered a tremendous tragic loss when five Buffalo, NY, firefighters were killed in the line of duty. These brave men answered their final alarm at the Chimera Radiator Co., located at North Division and Grosvenor streets...


On Dec. 27, 1983, our nation suffered a tremendous tragic loss when five Buffalo, NY, firefighters were killed in the line of duty. These brave men answered their final alarm at the Chimera Radiator Co., located at North Division and Grosvenor streets. The cause of this disaster was an illegally...


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In contrast, liquefied petroleum gas (LPG) is transported, stored and distributed in the liquid form, under pressure, and it is highly flammable. The gaseous propane and butane are compressed to change their physical state from gaseous to liquid, making storage and transportation easier and cheaper.

To liquefy the gases at 70 degrees Fahrenheit, the critical pressure for propane is 120 pounds per square inch gauge (psig); for butane it is 17 psig. This is the first major difference between the two families of gases (natural or LPG). Specifically, the LP gases possess a relatively high liquid to gas expansion ratio (propane 270:1; butane 230:1), while natural gas typically exists in the gaseous state (1:1).

The second major difference is the vapor density. Both of the LP gases are much heavier than air (propane 1.5, butane 2.0), which drastically changes the fire operations at an incident. LP gases are odorless, colorless and tasteless, and have ethyl mercaptan added to them.

Operations

In firefighting operations, two factors must be noted as soon as possible: the gas involved and the exact size of the leak. These two size-up factors probably will be the heaviest weighted factors in initial operations. Life safety of both the occupants and the firefighting forces is, of course, our first incident priority. Demand that the operating firefighters wear full protective clothing including self-contained breathing apparatus (SCBA). Rescue or extrication must be performed under the protection of a hoseline (air bleed off) supported by a dependable, adequate and continuous water supply. Move the affected people to a safe area, away from the gas cloud, as soon as possible. If the situation involves LPG, evacuation of a half-mile is not unreasonable. Don't overlook the bystanders; set up fire lines to protect them from the hazard zone.

Fire apparatus placement is one of the first mission-critical operational factors that must be considered. Extreme care must be used upon approach and a proper tactical placement of apparatus is a must. Remember, fire apparatus is an excellent ignition source as well as a very expensive exposure. Ideally, apparatus should be parked at least 500 feet away, on the upwind side, which means that you will be walking in from a distance, using an explosion meter to test the atmosphere distal to the leak.

LPG Tanks

When LPG tanks are involved in the incident, avoid the tank ends. The ends of the cylinders are thought to be the weakest because of the welds to the container and are most likely to fail. Apparatus as well as personnel should never enter a gas vapor cloud, for the danger is too great. If a victim is in a vapor cloud, disperse the cloud with a hoseline using fog spray, first, and then enter. Water supply is another factor to be considered when placing apparatus. If the gas leak is inside the building or involves an LPG cylinder, a reliable, continuous, uninterrupted water supply becomes a must.

If the gas leak is not burning, begin atmosphere monitoring, ignition source elimination, ventilation and leak control operations to resolve the problem. Proper gas detection equipment should be dispatched on the initial alarm to all gas leaks (perhaps the device is stored on a ladder truck or heavy rescue).

To briefly review the typical explosion meter operation, the meter indicates from 0 to 100% of the lower flammable limit of a particular gas to air mixture. In simple terms, when the average explosion meter reads 100%, the gas-air mixture has reached its lower flammable limit and is ready to ignite. Some meters will peg 100% and return downscale to indicate atmospheric concentrations above the lower flammable limit. Determine the vapor density of the gas involved, and use this information in both the detection and ventilation efforts. Thoroughly check and vent the areas (high — natural gas; or low — LPG) where the gas is expected to stratify as the priority area. Use and have an operational understanding of proper gas detection and air-monitoring equipment.

When to Ventilate