Tests show that surface-applied intumescent FRs prevent or delay ignition of wood products and reduce heat release. Three FR formulations were compared in cone calorimeter fire tests to virgin products (no FR), including MDF (medium density fibreboard), blockboard and pine. The FRs tested were intumescent, or intumescent plus phosphate ester. Heat fluxes of 35 – 80 kW/m2 were applied and time to ignition, peak heat release rate, average heat release rate, effective heat of combustion and gas toxicity (FTIR) were tested. The FRs resulted in either no ignition (including in all samples at 35 kW/m2) or considerably increased ignition time (2 -32x longer time). Peak heat release rate was reduced by 2 – 5 times. Toxic emissions were reduced when FRs prevented ignition (except for ammonia emissions from the intumescent) but were increased in cases of ignition, with carbon monoxide more than doubled in some cases, acrolein increased by 10-60 % and increased HCN.
“Thermal behavior and toxic emissions of flame retarded timber in cone calorimeter tests”, D. Tsatsoulas, Int. J. of Safety and Security Eng., Vol. 1, No. 1 (2011) 45–64 https://dx.doi.org/10.2495/SAFE-V1-N1-45-64