The main gas in CNG is methane.It also contains other hydrocarbons in small percentages.Compress CNG under high pressure (200BR).PNG is similar to CNG but supplied through pipelines for domestic use.LPG mainly consists of propane, butane, propylene, butylene.It is heavier than air, so it sits near the ground after leakage.But there is a possibility of danger in it.CNG, PNG, LPG, all three gases are used as energy sources.But if we talk about the major difference between them, then it is on the basis of source, structure and use