Toxic Species And Particulate Emissions From Wood And Pool Fires

Fire fatalities in the UK are attributed to smoke inhalation especially in dwellings. Another serious issue of great concern is the exposure to respirable particles of sizes less than 0.1µ in diameter found in smoke and soot and these have not been given much attention despite the health hazards associated with them. The main aim of this research was to quantitatively look at the toxic emissions (toxic gases and particulates) under different fire conditions for wood based materials relevant to residential fires and in pool fires relevant to industrial scenarios.
Different classes of wood (Natural, Processed and Plywoods) used in construction and furnishings were investigated under free ventilation conditions and restricted ventilation conditions using the standard cone calorimeter and the controlled atmosphere cone calorimeter modified to enable raw gas sampling. Pool fires (Diesel, Lubricating oil and olive oil) were also investigated using the freely ventilated standard cone calorimeter.
Pine wood crib and diesel pool of different sizes were investigated in a 5m3 fire test compartment at varying ventilation rates. Toxic concentrations were measured through a heated sampling line using a heated FTIR analyser, calibrated for 65 species.
An important finding was the overwhelming toxic gases produced by low temperature smouldering fires exceeding the impairment of escape threshold and the lethality threshold by a factor of 60-10 000 on an impairment of escape basis and a factor of 4-100 on lethal basis.
The real-time particle size, number and mass distribution from the burning fuels was obtained using the DMS 500 particle size analyser and this showed a bimodal distribution, representing a nucleation mode and an agglomeration/accumulation mode. The particle size distribution on a number basis showed a peak of 20 nm in the nano particle size range and a peak of 200 nm in the agglomeration range for most fires. These nano particles (20 nm) will penetrate the lungs in the event of fire, potentially leading to impairment of escape and eventually death due to the effects that fine particles have on the lungs thereby making them a major toxic hazard in fires. To the knowledge of the author, this is the first time that particulates in this size range (20nm and less) have been quantified from burning materials.
The modified cone calorimeter proved to be a good technique for realistic determination of toxic yields and particle size distributions when used with the heated FTIR and the DMS 500 analysers.