Q. Fire Retardant in Spray Foam
According to a university researcher I spoke with recently, polyurethane spray foam formulated for use in California is required to contain from 5 percent to 10 percent flame retardant by weight, and the size of the state’s market means that most other states get this same formulation. The researcher also claimed that flame retardants produce far more carbon monoxide and particulate smoke than untreated foam would, and are persistent and long-lasting in our bodies in an unburned state. Is it possible to avoid these problems by using foam without added fire retardants?
A.Rick Duncan, technical director of the Spray Polyurethane Foam Alliance (SPFA), responds: Like wood and many other building materials, foam plastic insulation is combustible and can give off particulate gases like carbon monoxide and hydrogen cyanide during a fire. At high concentrations, these gases pose an immediate threat to building occupants. For that reason, the ICC model building codes specify limits on flame spread and smoke development for foam plastics. Specific fire-performance requirements appear in Chapter 3 of the IRC and Section 2603 of the IBC.
While a few specially formulated foams may pass the fire test without flame retardants, most use phosphorus-based flame retardants to meet code. Getting the right mix is a balancing act, because the chemicals that slow flame spread can also increase the amount of smoke created during a fire.
Quantitatively, your source was in the right ballpark: The flame-retardant content of open-cell spray foam ranges from 15 percent to 25 percent of the B-side by volume, and from 5 to 10 percent in closed-cell foam.
Phosphorus-based flame retardants have undergone extensive industry and regulatory review, including scrutiny by the European Union. All are widely regarded as safe and nontoxic in the amounts used in SPF, and none are classified as carcinogenic, mutagenic, toxic to reproduction, environmentally persistent, or bio-accumulative. If you are concerned about a particular flame retardant, contact the foam manufacturer. Also, keep in mind that SPF flame retardants are entrained in solid polyurethane and are isolated from direct contact with building occupants.
As for fire performance, California’s requirements are no different from those of other states that have adopted the I-codes. Since all spray-foam manufacturers formulate their products for a national market, there are no state-to-state variations. A few SPF manufacturers offer special high-density SPF formulations for soil stabilization and other underground applications. These uses are not subject to the same fire performance requirements as insulation and roofing foams, so they may not contain flame retardants. In any case, these specialty products should never be used for building applications.
