Storing Group A plastics legally means meeting the highest-hazard requirements in NFPA 13 and the International Fire Code: denser sprinkler coverage, controlled rack heights and flue spaces, a high-piled combustible storage permit with detailed plans, and, in many cases, insurer standards that go beyond the code. Group A plastics storage requirements are the strictest in either standard because these materials release far more heat and burn faster than ordinary combustibles like wood or paper.1National Fire Protection Association. Commodity Classifications in NFPA 13 Treating this inventory like a lower-hazard commodity is one of the fastest routes to a coverage denial or a facility shutdown.
What Counts as a Group A Plastic
NFPA 13 places a material in Group A when its heat of combustion is much higher than ordinary combustibles and its burning rate exceeds Group B plastics.1National Fire Protection Association. Commodity Classifications in NFPA 13 The commonly stored materials on the list include ABS, acrylic, polycarbonate, polyester, polyethylene, polystyrene, and polyurethane. If your warehouse handles electronics housings, automotive parts, foam packaging, or plastic containers, you are almost certainly looking at Group A goods.
When a product is not specifically named in the NFPA 13 or IFC tables, the standard directs engineers to compare its burning characteristics against listed products and pick the closest match. In practice, commercial plastics that aren’t clearly Group B or C default upward to Group A treatment, because the consequences of underclassifying are severe. Group B and C materials (such as cellulose acetate, PVC with low plasticizer content, phenolic, and PTFE) fall outside the scope of what follows.2UpCodes. Examples of Commodity Classification
How Physical Form and Packaging Change the Requirement
The same polymer can carry very different protection requirements depending on how it’s packaged and stored. Three variables matter: whether it’s expanded or unexpanded, whether it’s cartoned or exposed, and whether it’s encapsulated.
Expanded Versus Unexpanded
Expanded (foamed) Group A plastics such as foam packing peanuts, Styrofoam cups, and expanded polyurethane insulation contain air pockets that accelerate ignition and intensify burning. Unexpanded forms are solid and dense, like molded polycarbonate panels or solid polyethylene bins. Both are hazardous, but expanded forms generally demand higher sprinkler density or additional in-rack protection than their solid counterparts.
Cartoned Versus Exposed
Cartoned storage means the plastic is fully enclosed in corrugated cardboard or paperboard. The cardboard absorbs sprinkler water, slowing fire spread. Exposed storage means the plastic is either unpackaged or wrapped in a non-absorbing material like plastic sheeting, and it is one of the most challenging fire scenarios in a warehouse. Exposed Group A goods often need in-rack sprinklers at storage heights where cartoned goods would still qualify for ceiling-only protection.
Encapsulated Loads
Encapsulated products are wrapped in plastic that covers the top and at least 75 percent of the sides. Shrink-wrapped pallets are the common example. Encapsulation traps heat and blocks sprinkler water from reaching the product, making fires harder to control. The IFC requires permit applicants to show the location of any encapsulated commodities on their floor plans, because these goods may need higher sprinkler density or additional in-rack protection beyond what the base commodity would otherwise require.3International Code Council. 2018 International Fire Code – Chapter 32 High-Piled Combustible Storage
Free-Flowing Plastics
One narrow exception runs the other way. Free-flowing Group A plastics like pellets, powders, flakes, or random-packed small objects can sometimes be protected as a lower-hazard Class IV commodity. The theory is that during a fire, these small items spill out of their containers and either smother the flames or fall away from the fuel load. The exception applies only when the material truly flows freely and fills its container without restraint.
Sprinkler System Design
Fire suppression for Group A plastics has to deliver enough water, fast enough, to overcome the extreme heat these materials produce. That drives choices about density, sprinkler type, and where heads have to be placed inside the racks.
Required Water Density
Density requirements depend on storage height, ceiling height, and whether the goods are expanded or unexpanded. For solid-piled, unexpanded Group A plastic at 20 feet of storage under a 32-foot ceiling, a stable pile requires 1.1 gallons per minute per square foot. An unstable pile at the same height needs 0.6 gpm per square foot. These flows are significantly higher than a standard commercial sprinkler system delivers, and many existing water supplies cannot meet them without supplemental fire pumps or storage tanks.
ESFR Sprinklers and K-Factors
Early Suppression Fast Response (ESFR) sprinklers are the standard tool for modern Group A protection. Rather than controlling a fire until the fire department arrives, ESFR heads are designed to suppress it by delivering large volumes of water at high velocity to penetrate the fire plume. The K-factor measures each head’s orifice size and flow capacity.
NFPA 13 limits K-14.0 ESFR sprinklers to ceiling heights of 35 feet when protecting rack storage. Larger-orifice K-22.4 and K-25.2 heads extend ceiling-only protection up to about 45 feet, with some specific criteria reaching 48 feet.4SFPE. The Return of the In-Rack Sprinkler The K-factor is not discretionary. Building height, storage height, and commodity dictate it. Specifying a K-14.0 head in a 42-foot building simply isn’t an option under the standard.
When In-Rack Sprinklers Are Required
Above roughly 48 feet, ceiling-only ESFR protection typically cannot handle Group A plastics, and in-rack sprinklers become necessary.4SFPE. The Return of the In-Rack Sprinkler In-rack heads sit inside the storage racks and deliver water directly at the fire’s origin rather than fighting through rising hot gases. For exposed Group A plastics, in-rack sprinklers can be required well below that 48-foot threshold. This is where the earlier distinction between cartoned and exposed storage has real financial impact: exposed Group A goods in tall racks can double or triple sprinkler installation cost compared to the same material stored in cardboard boxes.
Rack Layout and Flue Spaces
Even the best-designed sprinkler system fails if the racks are configured badly. Poor layout lets fire spread between arrays or blocks water from reaching lower rack levels.
Height Thresholds
Facilities typically use single-row, double-row, or multiple-row racks. NFPA 13 sets different protection criteria for rack storage of Group A plastics stored up to 25 feet versus over 25 feet, with storage above that height triggering additional suppression requirements.5UpCodes. NFPA 13 – Protection Criteria for Rack Storage of Group A Plastic Commodities Stored Over 25 ft in Height Exceeding the approved height without upgrading the sprinkler design can void insurance coverage overnight when an underwriter’s inspection catches it.
Flue Space Rules
Clear flue spaces do two things: they let heat rise fast enough to activate sprinklers, and they let water reach the lower rack levels. Single-row, double-row, and multiple-row racks must maintain a nominal transverse flue space of six inches between loads and at the rack uprights.6UpCodes. Flue Space Requirements for Storage Up to and Including 25 ft Longitudinal flues run parallel to the rack direction and also have to be maintained.
Flue space compliance is where many facilities lose points during inspections. Warehouse workers loading racks rarely think about a six-inch gap between pallets, and a few overloaded bays can compromise the whole system. The IFC requires flue space dimensions and locations to be documented on construction plans and visibly posted on a floor plan inside the facility.3International Code Council. 2018 International Fire Code – Chapter 32 High-Piled Combustible Storage
Solid-Piled and Palletized Arrays
Goods stored without racking, whether stacked on pallets or piled directly, face separate footprint limits that control the maximum pile volume for each array. The purpose is the same: ensure fire crews can reach the fire and stop it from spreading through an unbroken block of fuel. These limits have to appear on the construction drawings and on the posted floor plan.
Permits and Posted Documentation
Before storing Group A plastics at any significant scale, you need a high-piled combustible storage permit under the IFC.7International Code Council. 2021 International Fire Code – Chapter 32 High-Piled Combustible Storage Group A goods face the most demanding scrutiny in the application process, and the required construction documents go well beyond a simple floor plan.3International Code Council. 2018 International Fire Code – Chapter 32 High-Piled Combustible Storage
The submittal must include:
- A floor plan showing the locations and dimensions of all high-piled storage areas
- Usable storage height for each area, including the number of rack tiers
- Clearance between the top of storage and the sprinkler deflector for each arrangement
- Aisle width between each storage array
- Location and classification of all stored commodities, including any encapsulated goods
- Type and location of suppression and detection systems, including valve locations for ceiling and in-rack sprinklers
- Dimensions and locations of all transverse and longitudinal flue spaces
- Type, location, and specifications of smoke removal and curtain board systems
- Location of required fire department access doors
Once approved, a legible copy of the storage layout must be mounted on a wall inside the facility showing the rack layout, design storage heights, commodity types, clearances, aisle dimensions, and access door locations.3International Code Council. 2018 International Fire Code – Chapter 32 High-Piled Combustible Storage Fire crews rely on this posted plan during an emergency to understand what’s burning and where the water controls are. Permit fees and renewal costs vary by jurisdiction.
A fire marshal will inspect the facility to verify that conditions match the approved plans and that all safety equipment works. Inspectors focus on flue space maintenance, sprinkler functionality, and whether the actual storage matches the approved commodity classification. Mismatches between the plan and the racks are among the most common violations and can bring daily fines or forced closure until the facility returns to compliance.
Where Insurers Push Past the Code
Meeting the fire code is necessary but often not sufficient. Major property insurers, particularly FM Global, impose their own requirements for Group A plastic storage that frequently exceed the NFPA 13 and IFC minimums. Code compliance alone will not always protect you from a coverage denial.
FM Global’s Data Sheet 8-9 governs storage of Class 1 through 4 and plastic commodities and diverges from the standard codes in several ways. FM often requires higher water flow rates and longer system durations than NFPA 13 prescribes, which can mean larger fire pumps or additional water storage tanks. It may mandate in-rack sprinklers at lower ceiling heights than the code requires, and it enforces stricter clearance between the top of stored goods and ceiling sprinkler deflectors.8FM Global. Storage of Class 1, 2, 3, 4 and Plastic Commodities – Data Sheet 8-9
FM Global may also reject certain materials or equipment that meet NFPA standards, requiring FM-approved alternatives even when a UL-listed product satisfies the code. This is a particular issue with automated storage systems and high-hazard commodities. Facilities that design only to code minimums regularly discover during insurance audits that they need expensive upgrades to keep coverage. Designing to the insurer’s standards from the outset costs far less than retrofitting in-rack sprinklers or upgrading water supply infrastructure after construction is finished.