September 2026 Fire: How did the fire happen?

Return to: Frequently Asked Questions

• How did the fire happen?
  • Air monitoring during the fire
  • Air sampling during the fire
  • How was the fire put out?
  • How will you prevent this from happening again?
  • What are the emergency response protocols?
  • Why were there still energized batteries in the burned building?

How did the fire happen?

Damaged lithium-ion batteries may be unstable and can catch fire. While there are no active battery energy storage operations in the Moss Landing 300 building, inaccessible fire-impacted batteries are still inside awaiting safe removal following the January 2025 fire.

In this incident, one or more of the remaining intact battery modules started the fire, causing about 1,300 surrounding battery modules to burn. The exact cause of this incident is unknown. No work was being done at the time of the fire.

The battery removal operations were carefully planned to minimize risk as much as possible:

• Phase 1 work (complete): removed as many of the intact batteries as was safely possible; approximately 40,000 intact batteries were removed, de-energized and sent off-site to be recycled for their metals.
• Phase 2 work (in progress): prioritizes the removal of the remaining 2,500 intact batteries, 1,300 of which burned in the September 18 fire. These batteries are located in areas of the building that require the demolition of the north wall for access. This area could not be accessed in Phase 1 without putting workers at unacceptable risk.

EPA and Vistra have acknowledged that Phase 2 of the cleanup carries extra fire risk, and extensive safety and emergency response protocols have been in place to prepare for a potential fire or reignition. Throughout the remainder of the cleanup, we will continue to:

• Ensure safety and maintain emergency protocols
• Activate the emergency response plan if needed
• Prioritize the removal of intact batteries to further reduce the fire hazard
• Exercise fire prevention strategies.

Air monitoring during the fire

Monterey County posted air monitoring data from the facility perimeter and community on the Ready Monterey County website.

Air monitors around the perimeter of the property measure for:

• Particulate matter 2.5 (PM2.5, or “fine particulate matter”)
  • Some elevated PM2.5 readings were detected at the perimeter; however, they did not exceed the health-based standard. For more information on how EPA evaluates air monitoring data, see our FAQ "How are air results evaluated?"
  • Air quality remained in the "Moderate" to "Good" air quality category throughout the time of the fire and the hours and days following.
• Hydrogen fluoride (HF)
  • There were no detections of hydrogen fluoride, one of the contaminants of concern.

Following the established emergency protocols, EPA directed Vistra to expand the constituents monitored from PM2.5 and hydrogen fluoride to include: Volatile Organic Compounds (VOCs), percent oxygen, lower explosive limit (LEL), hydrogen cyanide (HCN) and carbon monoxide (CO) during the fire. These constituents did not exceed risk-based screening levels.

Monterey County posted air monitoring data from the facility perimeter and community on the Ready Monterey County webpage.

The Monterey Bay Air Resources District shares real-time air monitoring. Air quality conditions are dynamic, and the public is encouraged to visit MBARD’s webpage for the latest conditions.

Read about the difference between air monitoring and sampling.

Air sampling during the fire

Vistra conducted air sampling on September 18, 19, and 20 to test for asbestos and metals.

The air samples collected were sent to a laboratory for analysis and results will be shared with the public once they become available. Monterey County will post the air sampling results on the Ready Monterey County webpage.

Read more about air monitoring and sampling at Moss Landing.

How was the fire put out?

In this incident, North County Fire Protection District and Unified Command determined that the best course of action was to let the fire burn itself out because:

• If there is a fire impacting multiple battery modules, applying water may cause neighboring batteries to become unstable and catch fire
• Water is not commonly known to be effective at extinguishing a fire impacting multiple batteries in close proximity
• In most instances, the safest way to handle this is to let the fire burn itself out.

Fire crews used drones to monitor temperatures and capture overhead thermal imaging of the fire.

Water may be used with lithium-ion batteries in some situations. For example, if one battery begins to heat up during handling operations, personnel can isolate and cool the module to contain the reaction if safe to do so. Water tanks and/or battery isolation boxes are present on site for this use.

How will you prevent this from happening again?

• There is an ongoing risk of fire and/or smoke while handling and/or moving damaged lithium-ion batteries. To address fire and other risks associated with the battery cleanup, Vistra created an emergency response plan, which EPA provided input on and approved.
• The mitigation strategy for reducing the risk of fire includes:
  • Maintaining a private firefighting crew who continuously monitor the site and the Moss Landing 300 building
  • Continuing the removal of the remaining intact batteries as quickly and safely as possible. The risk of a substantial fire decreases as the remaining ~1200 intact batteries are removed from the site. These batteries remain in an area that requires careful stabilization, engineering and planning to safely access.

What are the emergency response protocols?

Several protocols can be activated depending on the circumstances of the emergency.

If a battery module overheats, it could:

• Be placed in an isolation box to cool down the battery with water and contain any heat
• Be submerged in a water tank to contain the reaction

If a battery module catches fire:

• If appropriate, all plant personnel will be evacuated to a safe area
• Emergency notifications will be made to include local first responders, partner agencies and EPA for coordinated response efforts
• A private firefighting crew that is on-site 24/7 would monitor the situation closely until North County Fire District arrives to assume command and direct firefighting approach as the lead agency
• Air monitoring and air sampling would be mobilized promptly. Air monitoring would be expanded to include VOCs, percent oxygen, lower explosive limit (LEL), hydrogen cyanide (HCN) and carbon monoxide (CO)
• A 24-hour fire watch would be conducted, following the event

For more information about Vistra’s emergency response protocols, see Appendix A of the  Administrative Settlement Agreement and Order on Consent: Moss Landing Complex (pdf) (5.12 MB, July 17, 2025) .

Why were there still energized batteries in the burned building?

There have not been any active battery energy storage operations at the Moss Landing 300 building since the January 2025 fire. No batteries in the burned building are connected to the grid. The energized batteries that started the September 2026 fire are batteries that were in the building when the initial January 2025 fire took place. The initial fire impacted the batteries to varying levels: some batteries were completely consumed, others were partially burned and many batteries, like the ones that burned in this fire, remained intact, still holding their charge.

Damaged batteries can retain an electrical charge. The remaining intact batteries were at 100% state of charge prior to the fire, and they likely still held a high state of charge despite the time elapsed.

Approximately 40,000 intact batteries were removed, de-energized and sent off-site to be recycled for their metals prior to this event. The batteries that burned were part of the remaining 2,500 intact batteries awaiting removal during Phase 2 cleanup.