While there are myths and misconceptions that compressed natural gas (CNG) is not as safe as other fuels, facts say otherwise. And, CNG has a number of properties that make it inherently safer than gasoline, diesel, and other alternative fuels. By Rob Minton
There are many misconceptions about how safe compressed natural gas (CNG) is as a vehicle fuel. This is the same fuel used to heat houses, clothes dryers, stoves, etc., but it is compress – usually to 3600 psi – when it is used as a motor vehicle fuel. And, while there are several factor to consider when deploying natural gas vehicles (NGVs), safety of the fuel and the vehicles that use it should not be one of them.
According to the U.S. Department of Energy’s Alternative Fuels Data Center, natural gas vehicles are actually safer than those powered by gasoline or diesel. The fact that CNG is lighter than air further enhances its safety.
Fuels such as diesel, gasoline, or liquefied propane gas (LPG)/propane autogas, which are heavier than air, pool on the ground, creating a fire hazard. If a CNG leak should occur, the gas will disperse rapidly upwards into the atmosphere and dissipate.
In terms of being a fire hazard, CNG is actually less volatile than gasoline. This is because CNG has a high ignition temperature – about 1,200 degrees Fahrenheit, compared with about 600 degrees Fahrenheit for gasoline. It also has very narrow flammability limits – that is, in concentrations in air below about 5 percent and above about 15 percent, natural gas will not burn. The high ignition temperature and limited flammability range make accidental combustion of CNG unlikely.