FM Global and NFPA 855 Special Storage

FM Global Requirements

FM Global is a commercial property insurer that produces its own engineering data sheets governing fire protection in insured facilities. FM Global requirements are typically more stringent than NFPA 13 and are contractually required for facilities they insure.

Key Data Sheets for Warehousing

Data Sheet	Subject
8-9	Storage of Class 1, 2, 3, and 4 Commodities
7-29	Rack Storage of Commodities
8-24	Automobile Storage
8-1	Plastic Storage (general)
5-32	Lithium-Ion Battery Storage

FM Global approval process: Insured facilities must submit sprinkler design drawings to FM Global for review. FM Approval (FM Approved suppression agents, heads, and systems) is a specific certification different from UL Listing. FM Global may require FM Approved products even when NFPA-compliant alternatives exist.

FM Global vs NFPA: Common Divergences

• FM Global typically requires higher water density (GPM/ft²) than NFPA 13 minimum
• FM Global may require in-rack sprinklers where NFPA ESFR would permit ceiling-only
• FM Global Data Sheet 5-32 sets specific requirements for Li-ion storage that go beyond NFPA 855 in some scenarios
• Some FM Global designs require FM Approved suppression agents (not just any listed system)

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NFPA 855 — Stationary Energy Storage Systems

NFPA 855 (Standard for the Installation of Stationary Energy Storage Systems) governs the installation, storage, and operation of battery energy storage systems in buildings — including Li-ion batteries used for forklift charging banks, grid-scale UPS, and large EV charging stations.

Why it matters for warehouses: Li-ion forklifts are rapidly replacing lead-acid. A large DC charging 50+ Li-ion forklift batteries simultaneously creates a significant aggregate energy storage that triggers NFPA 855 requirements.

Li-Ion Thermal Runaway Cascade

Thermal runaway occurs when a battery cell overheats, causing an exothermic chemical reaction that raises temperature further — spreading to adjacent cells.

Consequences:

• Rapid temperature rise (cells can reach 500–700°C)
• Off-gassing of toxic compounds including hydrogen fluoride (HF) — acute inhalation hazard
• Potential for sustained fire even after external ignition source is removed
• Conventional suppression (water, CO₂) may not stop thermal runaway once initiated

NFPA 855 Key Requirements

Energy storage thresholds (NFPA 855, 2023 edition):

• Systems ≤ 20 kWh: no special protection required beyond general electrical code
• Systems 20–600 kWh: fire separation, automatic suppression, and detection
• Systems > 600 kWh: additional separation, ventilation, and emergency response pre-plan

Protection systems:

• Automatic sprinkler protection (extended duration — water applied continuously for 60+ minutes due to sustained reaction)
• Early warning detection: smoke, heat, or off-gas (CO, VOC) sensors at battery level
• Ventilation to exhaust off-gases from the occupied space
• Emergency response pre-plan submitted to local fire department

Separation requirements:

• Li-ion storage rooms/areas separated from the rest of the warehouse by rated fire barriers
• Separation distance or barriers between battery units

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Cold Storage Commodity Classification

Commodity classification in cold storage environments is not intuitive — temperature affects how a fire behaves and how suppression systems function.

• Refrigerated (above 32°F): Standard commodity classification applies; sprinkler heads must be rated for the temperature range.
• Frozen (0°F and below): Commodity burns differently (slower ignition, but once burning, comparable heat release). Cold storage sprinkler systems require dry-pipe or pre-action designs to prevent freeze-up in the distribution piping.

Dry-pipe systems (air-pressurized pipe; water enters only when head activates) are standard for freezer DCs. Pre-action systems (dry pipe + electronic detection must trip before water enters) are used in highest-value freezer environments.

Classification of frozen food: Frozen meat, poultry, and seafood in standard corrugated packaging are generally Class II–III. Frozen products in high-density polyethylene (HDPE) bags or foam-insulated packaging may approach Class IV or plastics classification.

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Automated Storage and Retrieval Systems (AS/RS) — Fire Design Considerations

AS/RS present unique fire protection challenges:

• Access restriction: Firefighters cannot enter the rack structure during a fire; all suppression must be automatic
• Dense storage: Minimal flue spaces; limited horizontal and vertical penetration of water
• Complex rack geometry: Computer-controlled crane aisles with limited sprinkler placement options

Mitigation approaches:

• In-rack sprinklers at multiple levels within the AS/RS structure (coordinate exact locations with equipment vendor — must not interfere with crane travel)
• Early smoke/heat detection within the rack structure (not just ceiling-level)
• Smoke control system to exhaust combustion products
• Emergency crane shutdown protocol integrated with fire alarm system
• Pre-incident plan with local fire department (building drawings, AS/RS layout, water supply location)

High-bay AS/RS (>80 feet): Ceiling sprinklers alone are insufficient to reach fires at lower rack levels. In-rack and intermediate-level protection are required by most AHJs and FM Global.