Detection mechanisms of smoke compounds on homogenous semiconductor sensor films

The conductivity changes of tin oxide sensor films kept at 270 °C to various organic compounds originating during the combustion of wood were investigated by HRGC/SOMMSA (high resolution gas chromatography/selective odorant measurement by multisensor array). The films show high sensitivity and selectivity to organic compounds with hydroxyl groups. Phenolic structures lead to strong conductivity increases. Exposure to toluene, furfural and acetone does not change the film conductivity. The reaction of the films to beech wood smoke is primarily due to 2-methoxyphenol and 2,6-dimethoxyphenol derivatives with para-substituted alkyl and alkenyl groups, which originate in hardwood lignia. Both types of compounds occur in relatively high concentrations during smouldering and both are sensitively detected. In spruce wood smoke only reactions to 2-methoxyphenol derivatives occur. Reaction mechanisms are discussed in some details.