In a previous article, we talked about the generic hazards of dealing with compressed gases found in DOT Hazard Class 2. There have been two high profile incidents in the last several months illustrating the dangers of dealing with flammable gases in particular. In April, a gas leak in a store in Durham resulted in the death of the owner and injuries to 17, including a firefighter. In July, a home in Charlotte was leveled by an explosion caused by a gas leak inside the home. This incident resulted in the death of the homeowner. In September, a gas leak in a non-profit office building in Farmington, Maine destroyed the building and resulted in the death of a fire captain and injuries to six other people.
The intent of this article is not to speculate, point fingers or Monday morning quarterback the fire department responses in either of these incidents. Now is simply a good time to review the proper procedures for responding to a flammable gas leak, regardless of the circumstances or location.
Regardless of the time of day, time of year or weather, always wear your PPE. SCBA should be worn with the bottle on and the mask ready to be donned. The incident in Charlotte was captured on a neighbor’s door bell camera and showed how rapidly the situation can change when an explosion occurs. Your PPE will protect you from some of the blast and flying debris. SCBA should be worn any time you are investigating a gas leak inside a building. You could easily be overcome by the gas at higher concentrations. Your SCBA will also protect your respiratory tract should an explosion occur.
Do not be lulled into a false sense of security just because you can’t smell gas. Some gases are odorless while others are treated with an odorant such as mercaptan to make them more detectable. Just because you smell gas is not an indication that an explosion is imminent. The odor threshold for mercaptan is one part per million. You will smell it long before there is enough to create an explosive mixture with air. This is a safety feature that was added after the New London School explosion in New London, Texas in 1937. Almost 300 students and teachers were killed when odorless natural gas gathered in the basement area and was ignited by the boiler.
Look for the majority of flammable gases to settle into low lying areas such as basements, crawl spaces and sewers. Of all of the flammable gases, only hydrogen, acetylene, methane and ethylene are lighter than air and will rise. Ammonia is placarded as a non-flammable gas, but will still burn. Its flammable range is 15 to 25 percent. A flammable gas by definition has a flammable range that starts at less than 12 percent by volume in air. All other flammable gases are therefore heavier than air and will sink to the lowest levels.
The only way to detect the concentration of a flammable gas in air is with a combustible gas indicator (CGI). Some engine and ladder companies may carry this piece of equipment. In other jurisdictions, it might only be carried by the HazMat Team. No matter who carries it, at least one must be on the scene of every leak and preferably more than one. THERE ARE NO EXCEPTIONS TO THIS RULE! This is the ONLY way to do it.
Your nose is not sensitive enough to tell the difference between a flammable mixture and a non-flammable one. A carbon monoxide (CO) meter carried for CO emergencies will not give you a proper reading as they are designed to detect CO and CO only! I cannot tell you how many calls I have responded to as part of the HazMat Team or listened to on the radio where the first due company had a CO meter and told the HazMat Team that they could cut back to non-emergency traffic or cancel altogether because their meter “wasn’t detecting anything.” Of course it wasn’t! It was designed to detect carbon monoxide, not flammable gas! Use the right tool, for the right job and know the proper applications and limitations of your equipment.
When reading the amount of a flammable gas in air, do not be fooled by a reading stating that you are in an atmosphere below the Lower Explosive Limit (LEL). This reading can change in an instant should more flammable gas be introduced into the atmosphere. Also, do not make the mistake that you are safe in an environment if you happen to find yourself in an atmosphere where you are reading above the Upper Flammable Limit (UEL). This could quite possibly be the most dangerous position to be in. You are in an atmosphere where the fuel/air mixture is too rich, or too much fuel and not enough oxygen. More oxygen introduced into the atmosphere through something as simple as a door opening, the HVAC system activating or a strong breeze will reduce the fuel/air concentration into the Flammable Range. Once you are within the Flammable Range, you are in the middle of a perfect storm. The only thing needed to ignite the atmosphere is a spark. This spark could come from someone turning off a light switch, static electricity or from a tool scraping on metal.
Lastly, while responding it is important to request two things. Always ask for a wind direction so that you can approach the incident from upwind, keeping the flammable gas blowing away from you. Also, request the response of the local gas company for several reasons. These individuals have specialized training and will ultimately be responsible for repairing the leak. They have the tools and equipment to handle the job properly, including heavy excavation equipment that may be needed to dig up a ruptured gas line. They also bring another layer of air monitoring equipment to supplement that used by you or your HazMat Team.
Gas leaks have led to explosions that have injured and killed numerous firefighters and civilians over the years. Do not become a statistic by becoming complacent. Handle each of these emergencies in the matter that they deserve. They are dangerous hazardous materials incidents with the ability to kill and injure firefighters and civilians, not to mention the fact that they can cause millions of dollars in damage. They are not nuisance calls. Never forget that.