two full-scale protocols (a && b) were tested to determine the efficacy of cuprous oxide (cu2o) in reducing the concentrations of hydrogen cyanide (hcn) from flexible polyurethane foams (fpu) when thermally decomposed under realistic room conditions. in each protocol a test, a fpu cushion (untreated or treated with 0.1 cu2o) was cut in half, and the two halves were stacked on a load cell in a closed room. the ignition source was a hot wire placed between the two halves. rats were exposed to the decomposition products to examine the toxicological effects of the foams with and without cu2o protocol b differed from protocol a in that chairs were simulated by four fpu cushions attached to a steel frame; the treated fpu contained 1.0 cu2o; the cushions were covered with a cotton fabric; the chairs were ignited with cigarettes; and the burn room was open and connected to a corridor. in both protocols, the thermal decomposition progressed through nonflaming, smoldering and flaming phases and the concentrations of hcn and other gases were monitored foams used in the full-scale room burns were also examined under small-scale conditions (under flaming or a two-phase nonflaming/ramped heating mode) in the cup furnace smoke toxicity method. both atmospheric and reduced o2 conditions were studied. the small-scale tests showed an 87 reduction in the concentration of hcn and a 40 to 73 reduction in the toxicity of the thermal decomposition products when the cu2o-treated foams were tested. in the full-scale tests, the concentration of hcn was reduced 70 when the fpu contained 1.0 cu2o