CNG Vehicle Emergency Response: Fire Safety

CNG Vehicle Emergency Response (Fire)

• In case of a fire, attempt an emergency shut-down procedure: set the parking brake, turn off the engine, turn off the electrical system, and turn off the CNG fuel.
• If the fire is not extinguished quickly, the pressure relief valves will activate, releasing all the gas from the cylinders to the atmosphere.
• Do not apply water directly to CNG cylinders and PRDs, as this will prevent the PRDs from activating and can result in a catastrophic cylinder failure.
• If the CNG cylinders are not involved in the fire, the fire on the vehicle may be extinguished with normal response tactics.
• If fire is impinging on the CNG cylinders, the cylinders are on fire, or if the fire is fueled by an active leak, do not approach the vehicle. Allow the fire to burn while watching for secondary hazards.

Safety Precautions

• When approaching the vehicle, do so at a 45-degree angle.
• After the fire has been extinguished, there may still be pressurized cylinders in place.

Recommended Fire Department Response to Energy Storage Systems (ESS)

• Events involving ESS Systems with Lithium-ion batteries can be extremely dangerous.
• All crews must follow department policy and train on response to incidents involving ESS.
• Compromised lithium-ion batteries can produce significant amounts of flammable gases with potential risk of deflagration and fire.

Residential Setting Response

• Control power to the unit.
• Ventilate the area.
• Protect exposures.
• Contact manufacturer technical support as soon as possible.

Pre-Incident Planning

• Each manufacturer has specific response guidelines that should be made available to first responders prior to activation.
• Pre-incident planning should include guidelines for mitigation of the event, which may include a defensive operation.

Incident Actions

• Allow the battery to burn itself out, while applying water spray to neighboring battery enclosures and exposures to further mitigate the spread of hazards.
• Do not apply water directly to the affected enclosure, as this will not stop the thermal runaway event.
• Firefighters must wear full personal protective equipment, including SCBA with face-piece.
• If identified in pre-incident plan, shut off the unit/system by operating any visible disconnects or E-stops.

Incident Actions

• In pre-incident situations, allow the battery to burn out and apply water spray to neighboring battery enclosures and exposures to prevent the spread of hazards.
• Modify or establish department policy or standard response guidelines to ESS incidents, including guidelines for mitigation and management of the event.

Mitigation Strategies

• Apply water spray to neighboring battery enclosures and exposures to prevent the spread of hazards, rather than directly to the burning unit.
• Wear full personal protective equipment, including SCBA with face-piece, when responding to ESS incidents.
• Identify and shut off the unit/system by operating any visible disconnects or E-stops, if identified in the pre-incident plan.
• Isolate any PV system and protect exposures by shutting off multiple disconnects, including circuit breakers, knife-blade disconnects, or other switches.

Hazards and Risks

• Lithium ion batteries in thermal runaway or off-gassing can create hazardous atmospheres.
• Compromised lithium-ion batteries can produce significant amounts of flammable gases with potential risk of de-agration and fire.

Response Guidelines

• Follow department policy and train all staff on response to incidents involving ESS.
• For commercial or utility installations, follow pre-plan and do not enter the structure.
• For residential setting responses, control power to the unit, ventilate the area, and protect exposures.
• Contact manufacturer technical support as soon as possible in all cases.

Pre-Incident Planning

• Ensure pre-incident plans cover location, type, disconnect, and other contact information.
• Plans should provide rapid response resources for company officers specific to the area and region, including OEM emergency contact information.
• Maintain a safe distance from the unit involved (at least 300’ for large commercial systems).

General Guidelines

• Defensive firefighting is recommended, with water spray as the preferred agent for response to lithium-ion battery fires (lithium-ion is not water reactive).
• If a fire has not developed and only smoke is visible, take a defensive stance toward the system and be prepared to apply water spray.

Bump Testing and Gas Detection

• A "bump" test of a portable gas detector is performed to verify the functionality of sensors and alarms by briefly exposing the instrument to a known concentration of target gas(es) and verifying that the instrument responds accordingly.
• Data analysis is powered by 1 billion+ datalogged readings, 4.7 million+ bump test records, 2.5 million+ alarm events, 1.1 million+ calibration records, 27,000+ gas detectors, and 1,100+ customer sites.

Fire Safety and Reading Smoke

• Reading smoke is not a tactic but a tool to help make better tactical choices, allowing us to be more "intellectually aggressive" as opposed to arbitrary aggressiveness.
• The ability to read smoke has been lost in the emergency service world, but it's essential for predicting fire behavior, deciding tactics, and preventing firefighter injuries or deaths.

CNG Fuel System Components

• CNG fuel system components include cylinders, manual shut-off valves, pressure relief devices (PRDs), fill receptacles, and quarter-turn shut-off valves.
• Fuel cylinders are typically found on the roof, rear hatch, or behind the cab or frame rails, and are Type 3 or 4, pressure-contained with composite wrap, with no metal visible.
• PRDs are designed to vent system pressure and are thermally activated to vent gas between 212°F to 220°F (100°C to 104°C).
• High-pressure fuel lines are made of stainless steel tubing or flexible high-pressure hose, and are labeled with a yellow identifying tag.

CNG Vehicle Emergency Response

• In the event of an emergency, the procedure is to set the parking brake, turn off the engine, turn off the electrical system, and turn off the CNG fuel.
• If safe to do so, close the manual quarter-turn valve at the Fuel Control Module, and cylinder valves, and eliminate all sources of ignition.
• Use a combustible gas meter to monitor for potential fuel leaks, and open vehicle doors to introduce fresh air to prevent natural gas accumulation.
• If the vehicle is indoors, open building windows and doors to allow ventilation and avoid turning on any lights or electronics that may create a spark.

CNG Vehicle Emergency Response (Fire)

• Attempt the emergency shut-down procedure, and if a fire is not extinguished quickly, the pressure relief valves will activate, releasing all the gas from the cylinders to the atmosphere.
• Do not apply water directly to CNG cylinders and PRDs because it will prevent the PRDs from activating and can result in a catastrophic cylinder failure.
• If the fire is not involving the CNG cylinders, the fire on the vehicle may be extinguished with normal response tactics, but if the fire is impinging on the CNG cylinders, the cylinders are on fire, or if the fire is fueled by an active leak, do not approach the vehicle.