Compressed Natural Gas (CNG) is a fossil fuel alternative for gasoline (petrol), diesel, or propane/LPG. It is made by compressing the natural gas at standard atmospheric pressure, to less than 1% of its volume. It consists mainly of methane gas and it is tasteless, odourless, and colourless. It is extracted from domestically drilled gas wells or in combination with crude oil production. This Natural gas is used by over ten million vehicles everyday on the road. It is being used since 1990’s as an alternative clean burning fuel. Apart from powering the vehicles on the road, it is also delivered to most of the homes for purpose of heating water, cooking, and forced air heat. In order to use it in vehicles, this natural gas is compressed to 3000 or 3600 psi. Then it is pumped into the vehicle fuel tank for its consumption.

Compressed Natural Gas CNG is stored and distributed at a pressure of 200–248 bar (2900–3600 psi) in hard containers that generally come in cylindrical or spherical shape. It is also used in traditional gasoline internal combustion engine cars that were converted into the bi-fuel vehicles (gasoline/CNG). Natural gas vehicles are used increasingly in the Europe, Latin America, Asia-Pacific region, and America because of rising gasoline prices. CNG has been increasingly used in the response to rising fuel prices and environmental concerns. It is also used in transit and school buses, autos, pickup trucks, and trains.

It is also used in large fleet commercial vehicles and mass transit.

CNG has become regularly used in most of the countries around the world for addressing both air pollution as well as the high cost of diesel and petrol fuels. The blue diamond sticker is mostly used y in North America for indicating that the vehicle is powered by CNG. It acts as a fuel for an internal combustion engine similar to diesel engine. The engine is being designed specifically for CNG or it can easily be converted from diesel to CNG. It is also extremely safe fuel and it comes into extremely clean with no residue.