SPF (spray polyurethane foam), like most other organic materials, is combustible. Although SPFs are formulated with flame retardants to meet the requirements of various construction codes and minimum performance standards there is still a need to provide further protection from fire. All foams must undergo some common fire tests such as ASTM E84, UL 723 and others, to determine how fast and how far a flame will travel across the surface, along with how much smoke is produced when the foam is exposed to a fire. However, the flame spread and smoke developed indexes from these tests are used solely to measure and describe properties of products in response to heat and flame under controlled laboratory conditions. The numerical indexes are not intended to reflect hazards presented by SPFs or any other material under actual fire conditions when left exposed. When exposed to fire sources, such as residential fires, trash fires, welding arcs, cutting torches or red-hot metal, unprotected SPF can ignite and may result in a flash fire. Although burning SPF will form a surface layer of less flammable char, which can increase the fire resistance, the initial burning can produce combustible gases and black smoke. These combustible gases can accumulate and ignite resulting in flashover, a dangerous fire situation. Under these conditions, additional foam and other combustibles can become involved in the fire, creating additional combustible gases and feeding the fire. It is this initial flashover potential along with high levels of smoke production that model building codes require SPF to be covered by thermal barriers or ignition barriers (depending on the use of the space), or to have the SPF assemblies meet large-scale fire tests such as NFPA 286 designed to ensure sufficient time for occupants to escape a fire prior to a flashover situation. This egress period is critical to meet life safety goals for building occupants. The Spray Polyurethane Foam Alliance publishes great guides and documents to support the SPF industry, be sure to check out their SPFA-126 “Thermal and Ignition Barriers for the SPF Industry”
