FM Global DS 7-112: Lithium-Ion Battery Manufacturing and Storage Fire Protection

Lithium-ion battery manufacturing and storage is the fastest-growing high-risk industry of recent years. FM Global DS 7-112 addresses thermal runaway, reignition and explosion risk, and gives detailed sprinkler design criteria. This article summarises the FM strategy in practical terms.

The Risk

• Thermal runaway: the electrolyte begins to decompose as cell temperature rises, cathode reactions follow, and above a further threshold the cell ignites. Once started it grows uncontrollably.
• Abuse: mechanical (puncture, crushing), electrical (overcharge, short circuit) and thermal (high ambient temperature) — any of these can initiate runaway.
• Reignition: cells that have been extinguished can re-ignite hours or days later, so isolation and monitoring are essential.
• Explosion: vented electrolyte gases including carbon monoxide, hydrogen and hydrocarbons can create an explosive atmosphere in an enclosed space.

Protecting the Manufacturing Plant

• Coating and drying: solvent-based coating processes need HC-3 sprinklers with foam-water, and exhaust designed to NFPA 91
• Calendering and slitting: mechanical processes at HC-2
• Formation: the first charge and discharge cycle carries the highest runaway risk, requiring dedicated sprinklers, smoke detection and very early warning
• Ageing: long-duration monitoring in the holding area
• Explosion prevention: a high mechanical ventilation rate and hazardous area zoning

Storage Design

DS 7-112 maps lithium-ion storage by height and packaging type:

• Solid piled or palletised up to 1.5 m: sprinklers at 8.1 mm/min over 232 m²
• Open-frame rack up to 3 m: 12.2 mm/min with in-rack sprinklers added
• Open-frame rack above 3 m: ESFR K360 with in-rack sprinklers at every level — the most conservative FM position
• In plastic containers: sprinklers required even below 1.5 m, because runaway melts the container
• Cartoned: additional protection with a tighter height limit

Layered Early Warning

• Smoke and heat: aspirating smoke detection for early warning in storage and formation areas
• Gas detection: carbon monoxide and hydrogen monitoring, which catches venting before flaming
• Thermal imaging: automated cameras detecting temperature anomalies in the battery array
• Battery management system: cell-level voltage, temperature and current monitoring

The Insurer Position

Battery plants are large capital investments and carry international insurance, which means FM Global data sheets are typically taken as the baseline. What insurers look for:

• Sprinkler design, early warning and explosion prevention as an integrated package
• Internal separation, with the formation area and finished goods in distinct fire zones
• Fire service familiarisation and an emergency plan, because lithium-ion fires behave differently
• Annual survey with risk score tracking

Quick Checklist

• Hazard and sprinkler design set by production stage
• Storage design by stack height and packaging type
• ESFR K360 with in-rack sprinklers above 3 m storage
• Aspirating smoke detection with carbon monoxide and hydrogen detection
• Thermal imaging and battery management system monitoring
• High ventilation rate and hazardous area zoning
• Extended isolation and monitoring of extinguished cells

Frequently Asked Questions

Why is a lithium-ion fire different from an ordinary warehouse fire?

Because thermal runaway is self-sustaining: the cell generates its own heat and oxidant, so it does not depend on the surrounding air. That means conventional suppression controls the surrounding fire but does not stop the cell, which is why the strategy emphasises very early detection, cooling and containment rather than extinguishment.

What makes reignition such a problem?

A cell that has been through a thermal event retains stored energy and internal damage, so it can re-enter runaway hours or even days after the visible fire is out. This is why extinguished cells are moved to an isolated area with continuous thermal and gas monitoring, and why re-entry is governed by measurements rather than elapsed time.

How does storage height change the protection required?

Substantially. Palletised storage up to 1.5 m can be handled by ceiling sprinklers at a defined density. Open-frame rack up to 3 m needs a higher density plus in-rack sprinklers. Above 3 m, FM requires ESFR K360 with in-rack sprinklers at every level, which is among the most conservative positions in any data sheet.

Why is gas detection used alongside smoke detection?

Cells vent carbon monoxide, hydrogen and hydrocarbons before they ignite. Gas detection therefore gives warning earlier than smoke detection does, and it also identifies the accumulation of an explosive atmosphere, which is a separate hazard from the fire itself in an enclosed space.

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