Ver 1.0  August 25, 2026


Applications

All Hexagon® Agility® compressed natural gas (CNG) fuel systems


Description


Characteristics

1. Natural gas (methane) is flammable; however, it will only ignite when mixed with air at concentrations between 5% and 15%. CNG burns with a visible flame.

2. Natural gas is lighter than air and will typically rise and dissipate into the atmosphere when released.

3. Natural gas can form a flammable mixture with air under certain conditions.

4. To be stored efficiently, natural gas must be maintained at high pressure [typically 3600 psi (250 bar)] within a CNG fuel system.

5. Natural gas is an asphyxiant. At high concentrations, particularly in confined spaces, it can displace oxygen fand create a breathing hazard.

6. Natural gas is odorless, colorless, tasteless, and non-toxic. An odorant (ethyl mercaptan) is added to provide a distinctive “rotten egg” smell that helps detect leaks.


Precautions and Preventative Measures


 WARNING 

1. Risk of serious injury or death by fire or explosion.

► Any ignition source, including flames, sparks, electrostatic discharge, or extreme heat, can ignite natural gas, even when only residual CNG is present.

2. Risk of serious injury from high system pressure resulting in uncontrolled movements of loosened parts.

3. Risk of serious injury or death by asphyxiation from inhalation of CNG.

► In high concentrations, particularly in confined spaces, CNG can displace oxygen and create a breathing hazard. Symptoms of oxygen deficiency may include dizziness, loss of coordination, and loss of consciousness. Affected individuals may not recognize the danger before becoming incapacitated.


Always observe the following safety measures when working with CNG fuel systems:

1. Do not place or use fuel systems near any ignition sources, including flames, sparks, electrostatic discharge, or extreme heat.

2. Do not smoke or vape near the system.

3. When defueling, always connect the fuel system to an approved grounding point using approved grounding cables.

4. Always assume the fuel system and its components are under pressure until properly depressurized.

5. Whenever possible, perform work outdoors. Indoor work is permitted only if the fuel system has been properly defueled and the facility complies with applicable Authority Having Jurisdiction (AHJ) requirements.

6. Provide adequate ventilation when work must be performed in an enclosed area.

7. Fuel system venting must only be performed outdoors.

8. Inspect the fuel system daily for signs of leakage, including: unexplained pressure loss, audible hissing, bubbling at fittings or component connections, frost or ice formation on fuel system components or plumbing.

9. Perform leak checks as required.

10. Always use nitrogen to purge system contents. Never use compressed air.

11. Never use compressed air to clean any fuel system component.


For additional information on CNG properties, hazards, and safe handling practices, consult the applicable Safety Data Sheet (SDS) for natural gas and the current edition of U.S. DOT Emergency Response Guide (ERG) #115.


Refer also to ENP-084 First Responder Guide.







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