Inerting the System

WARNING: This page is about a different car, the 2017 Chevrolet Spark. However, it is still accessible from the selected car via links, so may be relevant.

If it is necessary to purge the gas system, only inert gases may be used which do not constitute an ignition hazard. An example of a suitable inert gas is nitrogen.
The system which has been depressurized from its normal pressure is then pressurized once with nitrogen at a pressure of 15 bar (218 psi) and discharged; it is then pressurized with nitrogen again in a second cycle, this time at a pressure of 10 bar (145 psi) and discharged (depressurized) again.
The draining procedures for CNG vehicles including flushing operations can be found under "Engine Controls/Fuel".