Risk of explosion caused by escaping natural gas or by overheated compressed-gas tanks when working on natural gas powered vehicles. Risk of frostbite to parts of the body caused by escaping natural gas and by touching components near the valves when emptying compressed-gas tanks. Risk of poisoning or risk of suffocation caused by inhaling natural gas. - AS00.00-Z-0018-01A

Remove any sources of ignition. Wear heat protective gloves. Ensure that the work area is adequately ventilated. 

Potential risks 

Risk of explosion 

There is a risk of explosion if natural gas escapes from the system (e.g. through leaks) or if the compressed-gas tank becomes overheated.

No smoking, fires or open flames:

• Near the refueling point,
• near the engine compartment
• near the gas reservoirs,
• in the vehicle parking hall or workshop.

Risk of frostbite 

When compressed-gas tanks filled with natural gas are emptied, the expanding natural gas cools down to such an extent that there is a risk of frostbite when coming into contact with components close to the valves.

Risk of poisoning and asphyxiation 

There is a risk of poisoning and asphyxiation if natural gas is inhaled when high gas concentrations are present in the surrounding air. Particular attention must be paid in this respect to the potential enrichment of natural gas in closed environments.

Safety precautions/instructions 

Maintenance and repair work may only be carried out by specially trained personnel.

Any vehicle fitted with a natural gas system and parked on the premises of the workshop must be provided with an easily visible warning of the presence of a natural gas system.

Natural gas is lighter than air and may under certain conditions build up in excessive concentrations in the air. For this reason, vehicles fitted with a natural gas system on which the gas shutoff valves are not closed and the gas lines are not emptied may only be parked at places

• at which an air exchange takes place at least 3 times an hour.

In workshops, adequate ventilation openings must be provided in the roofs of the shops to ensure that any escaping natural gas is able to rise up and escape to atmosphere without risk.

Before commencing work, ensure that all sources of ignition have been removed. Ensure adequate ventilation of the immediate area around the vehicle.

Adequate ventilation means an exchange of air at least 3 times an hour at a distance of 3 meters from the gas shutoff valve.

Close the gas shutoff valves at the compressed-gas tanks before commencing repair work.

After closing the gas shutoff valves, empty the gas lines by running the engine.

The gas lines are sufficiently emptied when the engine switches to gasoline operation or stops by itself after running at idle speed for several minutes.

Vehicles fitted with natural gas systems on which the gas shutoff valves remain closed and the gas lines have been emptied can be serviced in the same way as vehicles which operate with gasoline; provided that

• the gas shutoff valves remain closed,
• the gas lines are evacuated and
• the compressed-gas tank is not allowed to reach a temperature in excess of 60°C.

It is not permitted to carry out any work on vehicles fitted with natural gas systems if a risk of ignition is present unless special safety precautions have been taken, e.g. closing gas shutoff valves, to prevent gas escaping and to prevent a rise in pressure as a result of an increase in temperature in the natural gas tank or in the gas lines. If applicable, the gas lines must be emptied and the compressed-gas tanks be removed.

If there is a risk that tanks filled with compressed natural gas may acquire a temperature of more than 60°C when placed in driers for coating substances (e.g. when painting), they should be removed prior to drying.

After performing work at the components or gas lines of the natural gas system, a leak test must be carried out. The regulations regarding the leak test vary between countries. Please refer to the national legislation for the specific regulations.

The procedure for detecting leaks in a natural gas system must avoid any risk of igniting any gas which may flow out.

Leak detectors that can also perform gas measurements far below the explosion threshold are especially suited as gas measurement and warning devices. A leak detecting spray is used for precise location of leaks.

Natural gas can cause frostbite injuries. Protective leather gloves should be used if necessary.

Discharge area:

You should avoid discharging the gas to the atmosphere - if possible - because natural gas is a greenhouse gas. Furthermore, discharging may also be disturbing to the neighbors. If discharging cannot be avoided, the specifications of the vehicle or system manufacturer must be observed.

Emptying gas systems by means of discharging may only be performed outside. To empty the gas system, a marked area of approx. 10X10 m is required. No other vehicles may be located in this area during the process and no other work may be performed.

The discharge area should preferably be equipped with a lightning protection system (lightning rod). As an alternative, the workshop can prohibit the release of natural gas in the event of thunderstorm. The discharge area should at least have a way to ground the vehicle e.g. by using a steel rod planted in the ground.

Special considerations for CNG:

If the discharge area is partially or completely roofed over, you must ensure that the escaping gas can flow freely upwards.

Storage area for removed and non-inerted gas cylinders:

Removed and non-inerted gas cylinders should not be stored in the general maintenance and repair area. The storage area can be located outside. The storage area must be marked and access to the bottles can be limited, e.g. by means of a tightly-worked chain link fence. In any event, make sure that the gas can mix freely with the ambient air.