Spray foam insulation: Is it a fire hazard?
Read part 3 of this series: Spray Polyurethane foam manufacturer may face class-action lawsuit
There are two major types of fire risks associated with spray polyurethane foam. First, there are the problems associated with burning foam in the case of a house fire. Secondly, there is the chance that an improper spray foam installation will generate enough heat to cause a fire.
Almost all spray foam insulation sold in the U.S. contains flame retardant, because untreated foam is a fire accelerant. The National Association of State Fire Marshals addresses this issue in a report, titled "Bridging the Gap: Fire Safety and Green Buildings," and urges builders to follow fire safety codes carefully because of spray foam’s combustible properties:
"Most of the foam insulation products coming to the market are either polyurethane or expanded polystyrene foam, both of which are manufactured from petroleum derivatives. Untreated and exposed to elevated temperatures or flame, these foam products will burn vigorously, producing copious quantities of smoke, and spreading fire to other combustibles. Their burning characteristics require that they be manufactured with a fire retardant, be provided with a fire resistive barrier, or both."
The video below shows a test conducted by the National Fire Protection Association in 2011. The test compares three types of insulation: cellulose, fiberglass batting and spray foam. Unlike the other two insulations, the spray foam produces a heavy black smoke. It also quickly reaches “flashover” conditions, an intense heat that causes fire to spread rapidly. It's unclear if the “generic” spray foam in this test is treated with flame retardants or not.
When spray foam catches fire, it releases a number of dangerous chemicals. Safety guidelines published by Bayer Material Science, a manufacturer of spray foam, warns that burning foam can release "isocyanates, carbon monoxide, carbon dioxide, nitrogen oxides, and hydrogen cyanide, among other compounds." Contact with the smoke can cause asphyxiation, asthma and other long-term health problems.
The use of flame retardants in spray foam poses a difficult catch-22. On one hand, the addition of retardants adds to the toxicity of the foam. Yet on the other hand, untreated foam fuels fires and the resulting fires can be disastrous.
Improper installation can cause fires
The other fire hazard is produced by foam itself. The chemical reaction that occurs during spray foam installation generates heat in an exothermic reaction. The Bayer safety guidelines state that if foam is applied too thickly or if layers of foam are applied on top of each other too soon, "the foam may char, smolder, or burn."
Although these fires are relatively rare, they do occur. In 2011, Massachusetts state fire marshal Stephen D. Coan issued a memorandum stating, "at least three fires, one being a fatal fire, are believed to have been started during the application of spray foam insulation." The fatal fire caused the death of a spray foam installer. The ensuing investigations eventually found that spray foam was in fact the cause.
Next: Greener alternatives to spray foam insulation