ENP-084 Rev. E  April 8, 2024

This manual is a supplemental guide for public safety first responders to compressed natural gas (CNG) or liquefied natural gas (LNG) vehicle fuel system incidents.

It does not cover response tactics for liquefied petroleum gas (LPG or propane) or CNG vehicle fuel systems using Type 1 or Type 2 CNG cylinders.

This manual is not intended to replace any formal training on the proper response techniques, tactics, or procedures for responding to alternative fuel vehicle (AFV) accidents or incidents.

Hexagon Agility produces fuel systems for both CNG and LNG fuel vehicles for a variety of vocations and in several configurations. Please refer to the appropriate subsections for visual cues for vehicles of each fuel type.


Always refer to most recent version of the United States Department of Transportation (USDOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) Emergency Response Guide (ERG).

Always consult the National Fire Protection Association (NFPA) “Alternative Fuel Vehicles Training Program for Emergency Respondersand your own training programs for the latest information and best practices for CNG and LNG emergency response.

Table of Contents

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Warning Statements Used in this Guide    



I. Compressed Natural Gas and Liquefied Natural Gas Facts    

II. Compressed Natural Gas (CNG) Vehicles    

    1. CNG Vehicle Identification    

        1.1 CNG Vehicle Decals    

        1.2 CNG Vehicle Configurations and Visual Cues    

        1.3 CNG Vehicle Cylinders and Mounting    

        1.4. CNG Pressure Relief Devices (PRDs) and Vent Lines    

        1.5 CNG Fuel Management Module (FMM)    

    2. CNG Vehicle Emergency Response

        2.1. If a CNG Vehicle is Damaged or a Gas Leak Is Discovered

        2.2. In Case of a CNG Vehicle Fire    

III. Liquified Natural Gas (LNG) Vehicles    

    1. LNG Vehicle Identification

        1.1 LNG Vehicle Decals

        1.2 LNG Vehicle Visual Cues and Configurations

        1.3 LNG Fuel Control Components and Functions

2. LNG Vehicle Emergency Response

        2.1. If an LNG Vehicle is Damaged or a Gas Leak is Found

        2.2. In Case of an LNG Vehicle Fire

III. Hexagon Agility FleetCare First Responder Training

IV. References and Additional Information

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