Polyurethane foam is an organic plastic polymer. Therefore, it is combustible and will burn in the presence of sufficient heat, ignition, etc. With the addition of flame retardants, PU foams can be formulated to pass flame-spread tests (i.e., ASTM E84), which measure their resistance to combustion when exposed to an open flame. However, polyurethane foam is not intended to be used by itself as a firestop material, according to current accepted U.S. model building codes, such as ICC, NFPA, etc., which specify that through-penetration firestop materials be tested according to ASTM E814 (UL 1479). In order to pass firestop testing as the sole material being tested (no composite structures), a material must essentially be noncombustible, which is not the case for polyurethane foams.
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