Battery room fire at hosting company in Marcoussis, France
Feb 2020Published 12 Oct 2026Responsible editor: Chief Editor
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What happened
At about 04:00 on 11 February 2020 a fire broke out in a 20 square metre room used to store and charge batteries at a company specialising in telecommunications research and IT hosting in Marcoussis, Essonne, France. Of the 1,000 batteries in the room, 540 were affected. The batteries were fed through UPS inverters, so a residual voltage remained, and the instability of the components and the risk of extinguishing water damaging the inverters complicated the response.
CO2 extinguishers were ineffective. Firefighters filled the room with medium expansion foam through a roof opening, but the foam broke down quickly. In agreement with the company's manager, responders let the batteries burn out with the door kept closed, monitoring temperature with thermal cameras from outside. Nine firefighters were decontaminated and taken to hospital for blood tests, and two others suffered minor burns to their forearms. The fire was considered out 24 hours after the response began.
Contributing factors
Residual voltage remained in the batteries because they were fed by UPS inverters. Instability of the battery components and the risk of extinguishing water damaging the inverters complicated firefighting. CO2 extinguishers were ineffective and the foam broke down quickly. The source does not state the cause of ignition.
Lessons learned
- Battery rooms fed by UPS inverters need isolation procedures agreed in advance so that residual voltage is removed or controlled before firefighting begins.
- Operators should plan suppression methods for large battery arrays in advance, because CO2 extinguishers and foam may be ineffective.
- Sites should identify roof openings, ventilation points and drainage routes for responders, and protect power electronics from extinguishing water.
- Thermal camera monitoring from outside a battery room can support safe decisions when a controlled burn-out is the chosen response.
More lessons on worker safety and safe systems of work, fire suppression and firefighting, detection and monitoring, from every incident on the register.
Published 2026-10-12. Written from public reporting. Descriptive, not investigative. See the data accuracy disclaimer.
