Compressed natural gas filling stations (CNG filling stations) perform refilling of motor vehicles with CNG.
In the former USSR first CNG filling stations were constructed in 1939 in Melitopol, Gorlovka and Moscow. 30 high-capacity CNG filling stations supplying about 40 thousand vehicles with gas were constructed in the 1950s.
Unlike petrol and gas filling stations which only sell motor fuels, CNG filling stations are facilities where natural gas delivered via gas pipelines goes through comprehensive processing.
The CNG filling stations workflow includes:

• feed gas purification of liquids and mechanical impurities in a flash separator and filters;
• commercial gas metering;
• compression up to 25 MPa with refrigeration after each compression stage;
• gas dehydration in a dehydration unit;
• storage in batteries at the pressure of 25 MPa and distribution through gas dispensers at the pressure of 20 MPa.

A network of CNG filling stations is formed on the basis of standard vehicle series. More than 200 CNG filling stations were operational in Russia by the beginning of 2000. The network basically hinges on high capacity stations rated at 500 and 250 nominal refills per day.
A network of CNG filling stations includes:

• stationary AGNKS-500 stations (the figure determines the number of motor truck refills per day) which are designed for 0.4 to 0.6 MPa and 0.6 to 1.2 MPa inlet pressures;
• skid-mounted container-type AGNKS-250 stations;
• modular skid-mounted container-type AGNKS-125, garage CNG filling stations AGNKS-75;
• individual filling stations, etc.