CNG (Compressed Natural Gas)- Natural gas is stored in vehicle compressed form ( 200-250 bar pressure ). Major gas in CNG is methane. It also contains other hydrocarbons in minor percentage. Sulphar odourant is mixed in CNG to detect any leakage.
It is advantageous than LPG in characteristic that it is lighter than air so dissipates in air if any leakage occurs.
Pipelined Natural Gas
PNG ( Pipe lined Natural Gas) It is similar to CNG . Only difference that it is supplied through pipelines for household uses. LNG (Liquefied Natural Gas) This is form of Natural gas which is kept in super-cooled (cryogenic) temperature.
LPG (Liquefied Petroleum Gas) It is by-product during the processing and refining petroleum products. It mainly consists of propane, butane, polypropylene, butaylene.
It is heavier than air so settles on near ground after leakage.
It gives chances of hazard.