In case of gas leakage from CNG kit

Check out of the vehicle.
Do not start the vehicle. Push vehicles to a place out side the station in open Air.
Stop all activities in the vicinity, which can provide source of ignition, e.g. smoking, use of mobile phone etc.
Close down the cylinder valve master shut off valve in the CNG system to control the leakage.
Call CNG kit retrofitter to repair the same.