FM Global DS 7-112: Fire Protection for Lithium-Ion Formation and Aging Areas

In the cell finishing stage of lithium-ion manufacturing, cells are charged and discharged for the first time (formation) and then rested in racks until their properties stabilise (aging). FM Global DS 7-112 (October 2024, interim revision April 2025) expects a higher-than-normal number of thermal runaway events in these areas and gives them a protection scheme that is separate from, and more robust than, storage protection (§2.4.2).

Why Formation and Aging Are Critical (§2.4.2, §3.4.2, Appendix D.4)

• Formation is where the cell first undergoes charging and discharging to form the solid electrolyte interphase (SEI) layer; the process can last up to 15 days, with cells held in a high-bay storage system (Appendix D.4.1).
• During aging, cells are typically charged to 80–100% and rested in high-bay racks for an extended period, usually first at high and then at ambient temperature (Appendix D.4.2).
• The cells are unpackaged and thousands are stored extremely close together; defects introduced in earlier steps reveal themselves here (§3.4.2, Appendix D.4.1).
• The higher the level of protection, the fewer cells are involved, the less flammable and corrosive gas is generated and the less water is discharged, limiting nonthermal damage to other cells (§2.4.2).

Construction and Separation (§2.2)

• Formation/aging is separated from manufacturing and warehouse storage by at least one-hour rated, noncombustible fire walls (§2.2.2).
• Normally closed or automatic-closing FM Approved fire doors in the fire walls, and FM Approved penetration seals (§2.2.3–§2.2.4).
• Areas with a large number of finished cells are subdivided with noncombustible walls (§2.2.2.1).

Protection of Rack Arrangements (§2.4.2.1)

• Rack arrangements, including automated storage systems, are protected with in-rack sprinklers and barriers (§2.4.2.1.1).
• A maximum vertical distance of 1.8 m (6 ft) between in-rack sprinkler levels, with sprinklers above each column of storage (§2.4.2.1.5–§2.4.2.1.6).
• A horizontal barrier above each in-rack level: plywood of at least 10 mm or sheet metal of at least 0.7 mm (22 ga), with no gaps in the longitudinal flue and a maximum 75 mm gap at the uprights (§2.4.2.1.7).
• Vertical barriers of the same materials at rack uprights, no more than 1.8 m apart (§2.4.2.1.8).
• No cells stored above the top in-rack sprinkler and barrier level; if storage is placed there, the barrier is treated as a virtual floor and the commodity above is protected per DS 8-9. Cells stay within the rack footprint and do not overhang the barriers (§2.4.2.1.2–§2.4.2.1.3).

Hydraulic Design (§2.4.2.1.9–§2.4.2.1.13)

• At least 227 L/min (60 gpm) from each of the hydraulically most remote 6 sprinklers with one barrier level, or 8 sprinklers with two or more barrier levels.
• Quick-response, ordinary-temperature, K8.0 (K115) or larger in-rack sprinklers; in high-temperature aging rooms, a temperature rating suited to the room temperature.
• Where there are several layers of cells, water must be able to reach the bottom layer.
• Ceiling sprinklers are designed for the surrounding occupancy and do not need to be hydraulically balanced with the in-rack system.
• A 1,900 L/min (500 gpm) hose allowance and a water supply meeting the sprinkler and hose demand for at least two hours.

Bin-Box and Enclosed Chamber Arrangements (§2.4.2.2)

• Shelving with 4- or 5-sided bins, or enclosed charging chambers, get automatic sprinklers or water mist nozzles delivering water into each bin.
• At least 230 L/min (60 gpm) from each of the 6 most remote sprinklers; quick-response, ordinary-temperature, K8.0 (K115) or larger, with the thermal element inside and below the top of the bin.
• Only water mist systems FM Approved for formation and aging applications may be used.
• A 1,900 L/min hose allowance and a two-hour water supply.

Operations, Detection and Post-Incident (§2.3, §2.4.7.4, §2.8)

• A documented procedure for responding to a thermal runaway event in formation, aging and finished-cell storage areas (§2.3.1.4).
• Dedicated exhaust and FM Approved off-gas detection in charging enclosures and hoods (§2.3.1.2, §2.3.2.1).
• Cells that are not a finished product may be stored in ASRS only with the formation/aging protection of §2.4.2 (§2.4.7.4).
• A post-incident recovery plan covers reignition and the removal and disposal of damaged cells, with a fire watch until all potentially damaged cells have been removed (§2.8.2–§2.8.3).

Quick Checklist

• Formation/aging separated by at least one-hour noncombustible fire walls
• In-rack sprinkler levels no more than 1.8 m apart, with a horizontal barrier above each level
• Vertical barriers no more than 1.8 m apart; barriers of ≥ 10 mm plywood or ≥ 0.7 mm sheet metal
• ≥ 227 L/min from each of the most remote 6 or 8 sprinklers, quick-response K8.0 (K115) or larger
• 1,900 L/min hose allowance, two-hour water supply
• Thermal runaway response procedure and post-incident plan in place

Frequently Asked Questions

Why are formation and aging areas separated from the rest of the plant?

DS 7-112 expects a higher-than-normal number of thermal runaway events in these areas because this is where cells are first charged and discharged (§2.4.2). §2.2.2 therefore calls for at least one-hour rated, noncombustible fire walls between manufacturing, formation/aging and warehouse storage.

How are in-rack sprinklers designed in formation racks?

Under DS 7-112 §2.4.2.1, in-rack levels are no more than 1.8 m apart, with a horizontal barrier above each level and vertical barriers at uprights no more than 1.8 m apart. The design provides at least 227 L/min from each of the most remote 6 sprinklers with one barrier level, or 8 sprinklers with two or more levels, using quick-response sprinklers of K8.0 (K115) or larger.

What hose allowance and water supply duration apply?

Formation and aging areas need a 1,900 L/min (500 gpm) hose allowance and a water supply that meets the sprinkler and hose demand for at least two hours (§2.4.2.1.12–§2.4.2.1.13 and §2.4.2.2.8–§2.4.2.2.9).

Does DS 7-112 give ppm thresholds for gas detection?

No. It calls for FM Approved off-gas detection inside charging enclosures and hoods (§2.3.1.2) and ties emergency ventilation to gas detection or to 25% of the lower explosive limit for hydrocarbon gases (§2.3.2.1.4); it does not give CO or H₂ ppm thresholds.

How long should affected cells be monitored after a fire?

DS 7-112 does not set a fixed period. Affected batteries must be adequately cooled and moved to a safe location (§1.1.4); the post-incident plan addresses reignition, and a fire watch is kept until all potentially damaged cells have been removed (§2.8.2–§2.8.3).

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