Natural gas fueling comes in different forms: fast-fill or time-fill.
Fast-fill fueling is primarily used for retail applications where members of the public want to fill their tanks in the same manner as gasoline. The natural gas is pumped from the compressor to high-pressure storage tanks. A fast-fill system can fill a 20 gallon CNG tank in about the same time as a conventional vehicle and station.
Time-fill natural gas fueling is a great option for fleets that complete their daily route on one tank of fuel and return to a home base at night. In this circumstance, the vehicles can hook up to the time-fill station refuel slowly overnight. Fleets may prefer time-fill stations because they can have significantly lower installation costs because they don’t require as many high pressure storage devices or a dispenser (Source).
As long as codes are followed, just like gasoline or diesel fueling sites, natural gas is very safe during the fueling process (Source). There are many safety guidelines that are considered when developing infrastructure, including the National Fire Prevention Association's NFPA 52 Vehicular Gaseous Fuel Systems Code. Fire codes differ by jurisdictions, so it is important to contact the local fire marshal before developing a natural gas fueling station.
This tool can help you find Natural Gas fueling stations that are publicly available and closest to you.