Risk associated with the spray application of polyurethane foam

The use of polyurethane foam in thermal insulation is increasing rapidly. In most cases, the raw products consist of toluene di-isocyanate or diphenyl methane di-isocyanate and a polyol curing agent. We studied the isocyanate exposure of workers applying the foam in confined spaces. Frequent excursions above safe limits were found with levels up to and exceeding 0.08 ppm for personal sampling and 0.148 for area sampling. Since improper devices were worn, this represented a significant risk to health.