Standard industry formulations of flame retarded aliphatic polyamides, meeting UL 94 V-0, have been burned under controlled conditions, and the yields of the major asphyxiants, carbon monoxide (CO) and hydrogen cyanide (HCN) have been quantified. Although both the combination of aluminium phosphinate and melamine polyphosphate, and the combination of brominated polystyrene and antimony oxide, inhibit combustion reactions in the gas phase, this study shows that the phosphorus causes a much smaller increase in the CO and HCN yields than antimonybromine. The mechanisms of CO and HCN generation and destruction are related to the flame inhibition reactions. Both CO and HCN form early in the flame, and the OH radical is critical for their destruction. Crucial, in the context of the flame inhibition mechanism, is the observation that the phosphorus system reduces the H and O radical concentrations without a corresponding decrease in the OH radical concentration; conversely, the bromine system reduces all three of the key radical concentrations, H, O and OH, and thus increases the fire toxicity, by inhibiting decomposition of CO and HCN. Moreover, while the phosphorus flame retardant is effective as an ignition suppressant at lower temperatures (corresponding to early flaming), this is effect "switches off" at high temperatures, minimising the potential increase in fire toxicity, once the fire develops. Since flame retardants are most effective as ignition suppressants, and at the early stages of flaming combustion, while most fire deaths and injuries result from toxic gas inhalation from more developed fires, it is clearly advantageous to have an effective gas phase flame retardant which only causes a small increase in the toxic product yields.

Abstract. Four sandwich panel rooms were constructed as prescribed in the ISO 13784-1 test. However, the construction followed normal industry practice, and the panels were also subjected to the kinds of damage typically found in commercial premises, although such damage may not typically be concentrated in such a small room. The fire load was increased to simulate fires actually occurring in commercial premises by stepping up the propane burner output from the usual maximum of 300-600 kW, and by placing a substantial wooden crib in two of the rooms. The results

This study considers the demonstrated correlation between carbon monoxide and hydrogen cyanide in the special case of fire retarded materials. It shows that the combination of aluminium phosphinate and melamine polyphosphate causes a much smaller increase in the carbon monoxide (CO) and hydrogen cyanide (HCN) yields than the combination of brominated polystyrene and antimony oxide, although both fire retardants inhibit combustion reactions in the gas phase. The formation and destruction mechanisms of CO and HCN are considered. It is shown that both toxicants form early in the flame, and that the OH radical is critical for the destruction of both CO and HCN. Crucially, in the context of the flame inhibition mechanism, this suggests that the phosphorus system reduces the H and O radical concentrations without a corresponding decrease in the OH radical concentration, thus it is an effective gas phase flame retardant which only causes a small increase in the toxic product yields. Conversely, the bromine system reduces the H, O and OH concentrations, and thus increases the fire toxicity, by inhibiting decomposition of CO and HCN. Moreover, while the phosphorus flame retardant is effective as an ignition suppressant at low temperatures, this effect-switches off‖ at higher flame temperatures, minimising the potential increase in fire toxicity, once the fire develops.