Mining Publication: A 20-Liter Furnace Test Method to Determine the Combustion Gas Toxicity of Conveyor Belts

The U.S. Department of Energy Pittsburgh Research Center conducted experiments with mine conveyor belt samples in a 20-L furnace and in a laboratory fire tunnel to measure and compare the major toxic gas concentrations evolved during the combustion of the materials. The toxic gas concentrations, measured simultaneously through a multiport sampling device and treated as yield values, included hydrogen chloride (HO), hydrogen cyanide (HeN), oxides of nitrogen (NO_x treated as NO₂), and carbon monoxide (CO). The data obtained from the two experimental systems were in good agreement. Correlations were developed for the toxic gas yields as a function of the percentage of chlorine (for HO gas), nitrogen (for HCN and NO₂ gases), and carbon (for CO gas) contained in the original materials. The toxic gas yields were also used to calculate a toxicity index (TI) parameter to assess the potential gas toxicity of belt materials during a fire. Furthermore, the TI and the mass loss burning rate values were used to calculate a toxicity hazard (TH) parameter to estimate the toxic gas hazard produced by a burning belt in a ventilated system. Results show that polyvinyl chloride (PVC) belts released higher HCl concentrations because of the higher chlorine content; styrene-butadiene rubber (SBR) belts released higher CO, HCN, and NO₂ concentrations because of the higher carbon and nitrogen contents. The TI's, however, were greater for the PVC belts due primarily to the higher levels of HCl produced. The fire tunnel data indicate that the SBR belts can burn with higher mass loss rates than the PVC belts, resulting in a potentially higher toxic hazard (higher TH values) even though their TI values were lower than those of the PVC belts.