Non-Expanded Plastic as Class IV or Group A?

8/13/2026

I've got a question regarding commodity classification in a facility with a sprinkler system designed for Cartoned non-expanded Group A Plastics.

The owner wants to store high-weight non-combustibles inside plastic containers, see picture.

The total weight of plastics will not exceed 15% of the total weight.

Is there any chance the storage unit can be treated as a Class 4 commodity and raised to Cartoned Group A Plastics due to the plastic pallet?

Or is it necessary to treat the commodity as Exposed Group A Plastics because of the plastic container?

Thanks in advance.

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9 Comments

Peter H

8/13/2026 07:14:19 am

What type of plastic is the container made out of?

Glenn Berger

8/13/2026 08:33:06 am

As an AHJ told me early in my career - I see plastic; the entire system design must be for the exposed plastic.

Jesse

8/13/2026 08:37:41 am

Yeah I gotta go with Group A Plastic.

Joe Mc

8/13/2026 09:02:16 am

Unless you can prove that its class 4 go with Group A plastic.

I always ask my self do I want to make the NEWS for a place that burns down or had a small fire and the fire sprinkler system worked.

Jack G

8/13/2026 09:40:44 am

Under nfpa 13 plastic containers and the products inside are classified based on the resin type ( group A,B, or C) whether the plastic is expanded or non expanded and whether the containers are considered cartooned or exposed.
Group A: high hazard materials such as ABS, HDPE, polycarbonate, polyester, polypropylene, polystyrene, polyethylene.
Group B and C: B includes, cellulosic materials and acrylics..
C includes flouriplastics, melamine, and PVC , WITH low plasticizer content ( treated as class 3 commodities.
Expanded vs Nonexpanded:
Expanded plastics contain cellular or foam cavities trapping higher risk ( air) ; nonexpanded have a solid density like " molded storage bins ".
Cartooned vs exposed -- per nfpa 13 cartooned strictly as storage fully enclosed in corrugated cardboard or paperboard. Because group A plastics do not absorb water group A plastics inside or utilizing plastic containers are " generally " classified as exposed rather than cartooned.
Free flowing or cartooned: small objects, powders, or loose plastic items inside are considered free flowing which impact chapter 20 requirements.
First you must define the resin type for the above container.

Dan Wilder

8/13/2026 01:04:03 pm

That is a packaging not the commodity. The fact its plastic makes it no different than storing with plastic pallets (and looking at the bottom, that is what the pallet is, and likely reinforced) so unless whatever being stored is a Class I or II commodity, you're automatically into Group A.

Second issue is these looks like a big bin, and looking at the data sheets on it, there is no requirement to keep a lid so are you protecting for encapsulated or nonencapsulated? Other issue is bin box is defined as wood, metal, or cardboard...not plastic so as Jack pointed out, exposed.

Jimmy

8/14/2026 01:49:22 am

Thanks for all the replys,
It seems like Group A exposed Plastics would be the right commodity classification. (the container is Polyethylene - Group A Plastic).

But I wounder when the following would apply?

Extraction from NFPA13 2025 (20.4.3.2):

Storage Involving Group A Plastics

Once it has been determined that the stored commodity that requires protection contains Group A plastic, the process of determining the commodity class, although sometimes confusing, can be broken down into simple steps.

The critical components used to determine the commodity classification are individual storage units (e.g., unit load, pallet load), the primary packaging material, and the pallet type and composition. A simple correlation can be formed—an individual load (such as a pallet load) takes up a volume of space and has a certain total weight. As the amount of plastic that makes the load increases, the severity of the fire and the protection criteria will also increase.

Confusion often occurs when it comes down to the percentages by weight or volume of Group A plastic that differentiate classification levels from a Class III all the way to an exposed expanded plastic. It is the weight and volume of the load, not the individual items in the load, that determine the classification.

Weight. The weight is often misapplied to the individual product rather than to the total load. Simply imagine the load (usually on a pallet) sitting on a scale—that is the total weight of the load. Some loads are individual units as they stand on their own, but the concept is the same: the total load that will burn as a unit has a weight. The weight of the total quantity of unexpanded Group A plastic will be measured against the total weight of the load to determine the percentage of plastic weight. Therefore, to calculate the percentage of weight or volume of the product, the following factors must be included:

- The product itself
- Internal packaging and material, such as any dividers or protective material
- External packaging material (if any)
- Pallet or shipping aid (if any)

Nimal Tissa Wijetunga

8/16/2026 11:02:47 am

As per the information provided in the question, this must be considered as Group A plastic (Exposed/unexpanded) for Wet pipe Sprinkler design in line with requirements of NFPA 13.

Franck

8/20/2026 08:49:12 am

It is to be considered as group A plastic, because the fire will predominantly develop and spread on the outside and the sprinkler will work ob the outside as well.
In the most optimistic evaluation, it would be similar to an encapsulated commodity, which is already a greater hazard than a simple class IV commodity.

An important thing to consider: when stored, the upper lid needs to be present. If not, it will be considered as open top container and the sprinkler systems are really challenged with open top containers (water from sprinklers remains in the container rather than flowing around and prewetting adjacent loads)

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Non-Expanded Plastic as Class IV or Group A?

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