CNG (Compressed Natural Gas) is common natural gas from the distribution network, which for use as a fuel is compressed by a compressor in a CNG filling station at a pressure of 200 bar and in this compressed form is filled as CNG into vehicle pressure vessels. CNG consists mainly of methane (about 95%) and higher hydrocarbons with a small amount of inert gases. CNG achieves higher energy efficiency, also due to the high octane number, which is close to 130. The quality of CNG is regulated in the standard STN EN ISO 15403-1.
Under current European legislation, all Member States are required to label dispensers at petrol stations with a single symbol. This is linked to meeting environmental requirements for reducing CO2 emissions from fuels and promoting the use of alternative fuels. CNG is also an alternative fuel, as less pollutants of nitrogen oxide NOx, carbon monoxide CO, particulate matter PM and carcinogens are released into the air during CNG combustion.
At petrol station is CNG labeled by a diamond symbol and the letters CNG.