Researchers at commercial property insurer FM began testing lithium-ion batteries in 2020 to answer a critical question with implications for data centers, battery energy storage systems, and other scenarios: Can off-gas detectors provide early warning of battery fires and explosions?
Led by senior research engineer Sujit Purushothaman, the team subjected batteries to overheating and overcharging inside a secure lab chamber. They waited for the batteries to vent gases – a precursor to thermal runaway – and monitored whether detectors could catch this warning in time. The answer they found was yes.
“If someone makes a claim, our job is to evaluate that claim,” Purushothaman said.
Purushothaman’s paper, presented at a 2024 IEEE conference, confirmed that off-gas detectors can, in some cases, provide a five- to 20-minute window before thermal runaway begins. This was the first independent evaluation of the technology, validating its potential to prevent catastrophic battery failures.
How the research was conducted
Thermal runaway is a chain reaction in damaged or defective batteries that leads to fires and explosions. Once thermal runaway starts, it can’t be stopped.
Off-gas detection works by sensing electrolyte vapors that a lithium-ion battery gives out in the minutes before it’s about to go into thermal runaway.
In conducting this research, Purushothaman’s team overcharged or overheated batteries in a testing chamber outfitted with off-gas detectors. Those detectors were able to pick up on the presence of off-gas vapors when the cell vented them. Shortly after the detectors went off, Purushothaman’s team stopped overcharging or overheating the batteries – and those batteries didn’t end up going into thermal runaway.
Who benefits from off-gas detection?
Off-gas detection is especially valuable in environments with high lithium-ion battery exposure. Erik Verloop, FM principal engineer for renewable energy, emphasized that it is relevant for battery energy storage systems (BESS) and data centers.
Modern data centers increasingly rely on lithium-ion UPS systems, which pose risks of fire and toxic gas release. High-capacity BESS installations located in densely populated or enclosed environments face heightened thermal runaway risks.
FM Approvals: a first for off-gas detection
In 2025, FM Approvals – the third-party, internationally recognized testing and certification arm of FM – certified the first lithium-ion off-gas detection system: Nexceris’ Li-ion Tamer (LT-SEN-M). Approvals also certified the Gen2+ system, a cost-effective solution for small battery enclosures.
“It’s a big deal, because everything up to now has been focused on what to do after the fire starts,” said Patrick Byrne, operations vice president, group manager at FM Approvals. “Now you’re actually focusing on what to do to prevent the fire from starting.”
For more property resilience insights, visit the FM website.
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