Commercial CNG Vehicles: A Whole New Danger for Responders

BY STEVE SMITH

Commercial vehicles fueled by compressed natural gas (CNG) are everywhere in North America, from rural America to the major metropolitan cities. You have probably seen one but did not realize it or the potentially serious situation posed if that vehicle were on fire. Below, I will cover the properties of natural gas; identifying commercial CNG vehicles; how, where, and when such vehicles are refueled; how the CNG system is built and installed on different commercial vehicles; and, most importantly, what to do and what not to do if a commercial CNG vehicle is on fire, based on industry and government agency recommendations.

Natural gas is a combustible mixture of hydrocarbons. Although natural gas is primarily methane, it can also include ethane, propane, butane, and pentane. In its purest form, such as the natural gas delivered to your home, it is almost pure methane. Methane (CH4) consists of one carbon atom and four hydrogen atoms. The distinctive “rotten egg” smell of natural gas is mercaptan, an odorant added to it before it is delivered to the user to aid in detecting any leaks. Natural gas has a specific gravity of 0.55 to 0.64 (air = 1.00), which makes it lighter than air. According to the federal Environmental Protection Agency, compared to gasoline-fueled vehicles, CNG-fueled vehicles’ carbon monoxide emissions are 90 to 97 percent less, and carbon dioxide emissions are 25 percent less. Nitrogen oxide emissions can be 35 to 60 percent less, and other nonmethane hydrocarbon emissions can be 50 to 75 percent less.