Compressed natural gas, or CNG, is natural gas under pressure which remains clear, odorless, and non-corrosive. Although vehicles can use natural gas as either a liquid or a gas, most vehicles use the gaseous form compressed to pressures above 3,100 pounds per square inch.
Compressed Natural Gas (CNG) is made by compressing natural gas (which is mainly composed of methane, CH4), to less than 1 percent of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 20–25 MPa (2,900–3,600 psi), usually in cylindrical or spherical shapes.
When Compressed Natural Gas (CNG) is released it mixes with air and becomes flammable but only if the blend is within 5-15 percent natural gas. However, if the blend is less than 5 percent natural gas it does not burn as there is no enough oxygen. It is produced both domestically and worldwide at comparatively low cost and it is cleaner than diesel fuel or gasoline. The placement and cost of fuel storage tanks is the biggest barricade to quicker and wider adoption of the Compressed Natural Gas as a fuel.