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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Ventilation will likely be required early into the alarm. Use explosion-proof equipment, making all electrical connections away from the gas leak in a fresh-air area. Use the circuit breaker at the generator or make the final electrical connections at the apparatus and avoid using on/off switches in a combustible atmosphere. If the explosive range has exceeded the upper flammable limit (too rich to burn) by ventilating, the mixture will pass through the entire explosive range. Proper precautions must be taken if this is the case. Eliminate ignition sources and have hoselines ready as a minimum.

Controlling the flow of gas can range from a simple to a complex operation. A proper selection of tools and leak plugs will be helpful. Departments should develop pre-plans for facilities that have extensive or unusual gas equipment. This information must be easily accessible and available for rapid fireground use. When you are ordered to shut down any type of gas service, make an earnest attempt to isolate the gas supply as close to the leak as possible. When this is accomplished, the leak will subside more quickly; an important factor, especially with LP gas products (remember the high expansion ratios). This step will avoid unnecessary disruptions of gas service to unaffected customers. For example, if a gas range is leaking in an apartment house, use the gas cock on the leaking appliance rather than the meter serving the entire apartment building. Generally, control of gas at street valves is performed by the local gas utility employees and not by the fire department.

BLEVE Concerns

In situations where the leak has ignited, deploy regular structural firefighting tactics. However, do not attempt to extinguish the burning gas as it may cause an explosion. Fully protect the exposures to the gas leak, and extinguish the gas leak by stopping the flow of gas. If the flames are impinging on an LPG cylinder, consider the BLEVE (boiling liquid expanding vapor explosion) potential. Some factors that can help evaluate the BLEVE potential are:

  1. Flame impingement on the vapor space of a cylinder. Without cooling water, this situation will stress the steel until failure occurs.
  2. Flame plume at the relief valve is intense or increases intensity. This valve opens at 250 psig, and the higher the internal pressure, the higher the flame plume will grow.
  3. Noise level at the relief valve is intense or increases intensity. Noise accompanies the flame plume for the same reasons.
  4. Change in tank color or shape. The metal of the cylinder can take on a white or red-hot appearance. Also, depressions in the tank shell may appear. When the cylinder shows this type of stress, failure will probably be imminent.

If any signs of a BLEVE present themselves, evacuate everyone using a minimum of a one half-mile radius. Establish incident command as soon as possible. Command must consider such factors as personnel, equipment, adequate and continuous water supply, evacuation and liaison with the local gas company. If the incident is large enough (three companies or more), command should consider establishing sectors.

Summary

The safe handling of a utility gas incident requires a blend of skills and knowledge before and during the incident. Consult your local or state training agencies and the local gas companies to provide realistic gas emergency drills and training programs. Review available case studies, which may be useful if a similar incident occurs in your jurisdiction. Finally, perform pre-fire surveys and use the data to better handle the actual incidents and to conduct in-station drills. Use all the resources possible to prepare and protect you and your members at gas leaks and related incidents.

DENNIS L. RUBIN, a Firehouse® contributing editor, is chief of the District of Columbia Fire and Emergency Medical Services Department. Previously, Rubin was chief of the Atlanta, GA, Fire and Rescue Department. He holds a bachelor of science degree in fire administration from the University of Maryland and an associate in applied science degree in fire science management from Northern Virginia Community College, and is enrolled in the Fire and Emergency Management Administration program at the graduate school of Oklahoma State University. Rubin is a graduate of the National Fire Academy's Executive Fire Officers Program, is a Certified Emergency Manager (CEM) and has obtained the Chief Fire Officer Designation (CFOD) from by the International Association of Fire Chiefs. He is an adjunct faculty member of the National Fire Academy since 1983. Rubin is the author of the book Rube's Rules for Survival.

Type Gas NATURAL GAS LIQUEFIED PETROLEUM GAS (LPG)
Methane Propane Butane
Source: Author's research
Chemical Symbol CH4 C3H8 C4H10
Expansion Ratio Gaseous State 270:1 230:1
Vapor Density 0.6 1.5 2.0
Lower Flammable Limit (LFL) 5.0% 2.2% 1.9%
Upper Flammable Limit (UFL) 15.0% 9.5% 8.5%
Odor Odorless Odorless Odorless
Color Colorless Colorless Colorless
Odorant Ethyl-Mercaptan Ethyl-Mercaptan Ethyl-Mercaptan
Boiling Point Gaseous State -44°F 31°F
NFPA 704M System 1-4-0 1-3-0 1-3-0
DOT Identification 1972 1075 1075
Internal Cylinder Pressure at 70°F Gaseous State 120 psig 17 psig