Toxic Emissions from Processed Wood in Cone Calorimeter Tests

Despite the large number of deaths in fires due to exposure to toxic gases generated in the fire, there are no toxic gas requirements to be met for fires in any materials used in buildings. Only visibility obscuration by smoke in standard fire tests is required to be measured for building materials. This work investigated the toxic gas emissions from 3 different types of processed wood; Oriented Strand Board (OSB), Medium density fiberboard (MDF) and Chipboard faced with white melamine (CFM). The standard cone calorimeter was used for these tests with “raw” (predilution) gas sampling, using an 80mm diameter chimney mounted on top of the cone heater exit. Heated gas sampling and heated Gasmet FTIR toxic gas analysis was used with a 20- hole mean gas sample probe at the conical heater outlet plane. Each wood sample was exposed to the conical heater of the cone calorimeter radiating at 35kw/m 2 and the ignition delay for the 3 samples was 69 s (OSB), 142 s (CFM) and 54 s (MDF). Carbon balance equivalence ratios showed that rich mixtures occurred in some of the tests, indicating that some features of confinement were found in the raw gas analysis. These rich mixtures produced high concentrations of toxic gases. The 3 samples had similar peak HRR, but the time variation of HRR was different with the CFM having a slower growth of the fire to peak HRR. The glued surface and the manufacturing process introduced about 5% of organic nitrogen compounds into MDF and CFM and this produced very high levels of HCN immediately after the fire started. OSB had 1/10 the level of organic nitrogen than CFM or MDF and the HCN levels were much lower. For OSB formaldehyde and acrolein and were four times higher than for CFM and MDF and dominated the toxicity immediately after the fire started. The most important toxic species for all three processed woods were CO, acrolein, formaldehyde and benzene on both an LC50 and COSHH15min basis, which is used as an indicator of impairment of escape.