Group C is the NFPA 13 plastics group with the lowest heat release. Products made of these plastics are protected as Class III commodities, to the same criteria as wood and paper goods.
Quick reference
| Item | Value |
|---|---|
| Plastics group | Group C |
| Treated as | Class III commodity |
| Main materials | Rigid/low-plasticiser PVC, PTFE, PCTFE, PVDC, PVDF, PVF, melamine, phenolics, urea formaldehyde |
| FM Global DS 8-1 | Generally treated at Class 3 level; confirm in DS 8-1 |
| Typical protection | Class III criteria: CMDA, CMSA or ESFR |
What it is
Group C plastics are materials that are hard to ignite or release relatively little heat, because of halogens (chlorine, fluorine) in their structure or because they are thermosets. The NFPA 13 list mainly includes the fluoroplastics PTFE and PCTFE, melamine, phenolics, PVC with up to 20% plasticiser, PVDC, PVDF, PVF and urea formaldehyde. Products made of these materials are protected as Class III commodities.
Typical examples
- Rigid PVC pipe, fittings and window profiles
- PTFE gaskets, seals and semi-finished stock
- Melamine tableware and kitchenware
- Phenolic electrical components and laminates
- PVDF and PVDC films and pipes
How packaging and plastics change the class
A Group C product is Class III on its own, but packaging and ancillary materials can quickly spoil that. If rigid PVC pipe bundles are wrapped in PE film, fittings are bagged in PE and protected with Group A foam, the commodity moves to Class IV as soon as the Group A share passes 5%. Plasticiser content is another threshold for PVC: highly plasticised flexible PVC above 20% (such as some soft hoses and cable sheaths) is Group A.
Protection approach
The protection approach is the same as on the Class III page: CMDA, CMSA or ESFR according to storage height, rack type and aisle width, with in-rack sprinklers for tall or solid-shelf layouts. The corrosive and toxic gases (e.g. HCl) that halogenated plastics produce in a fire do not change the sprinkler design, but they must be addressed separately for smoke control, occupant safety and post-fire damage.
FM Global equivalent
FM Global DS 8-1 generally treats materials corresponding to Group C at Class 3 level. FM may assign a different class depending on product and packaging; on FM-approved projects verify against DS 8-1.
The commodity class depends on what goes into the warehouse today. The commodity and storage arrangement assumed in the design report should be recorded in writing and rechecked whenever operations change. For the overall framework see NFPA 13 commodity classification, and for a quick check on whether ESFR can be used, the ESFR suitability checker.
Common site mistakes
- Putting every type of PVC in one group; flexible, highly plasticised PVC is Group A.
- Ignoring the PE film and bags around pipe bundles.
- Grouping PTFE with other fluoroplastics such as ECTFE or FEP.
- Designing a Group C product as Group A because ‘it is plastic’, creating unnecessary water demand.
- Neglecting smoke control and corrosion risk in a halogenated plastics store.
Frequently Asked Questions
What class is a PVC pipe warehouse?
Rigid PVC pipe is a Group C plastic and is protected as a Class III commodity. If the Group A plastic share in the packaging exceeds 5%, the class rises.
Which group is PTFE in?
PTFE and PCTFE are Group C. Other fluoroplastics such as ECTFE, ETFE and FEP are Group B.
Why is Group C protected like Class III?
The heat they release when burning is close to that of cellulosic materials. NFPA 13 therefore treats Group C plastics as Class III commodities.
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Download SprinkCalc on the App StoreNFPA 13, Standard for the Installation of Sprinkler Systems (current edition) · FM Global Property Loss Prevention Data Sheets (FM Global DS 8-1). This page summarises the definitions in our own words; for design densities, areas and height limits the edition in force and the decision of the authority having jurisdiction govern.