New safety issues when moving from liquid fuels to natural gas

Natural gas (NG) is produced whenever organic matter is decomposed in the absence of oxygen. The main constituent of natural gas is methane. In contrast to liquid fuels, methane has a boiling point far below normal ambient temperatures. Even the critical temperature is well below ambient. Therefore natural gas must be stored either as compressed natural gas (CNG) at very high pressures at ambient temperatures, or as liquefied natural gas (LNG) at very low temperatures. The basic safety issues are caused by loss confinement of either CNG or LNG. In both cases the issues are: global greenhouse effects of natural gas (methane); local fire and explosion hazards; and local asphyxiation hazards due to reduced oxygen content in the atmosphere breathed when air is mixed with methane. (author)