The “hood method” of measuring emissions of rural cooking devices

The potential for the forced extraction of flue gases to change the combustion characteristics of unvented biomass-burning cooking devices is assessed. The performance of three stoves with different air inlet characteristics was measured using three hood extraction rates. These extraction rates were selected between the boundaries of being sufficiently low to have no visual impact on a flame at the height of the stove and of being high enough to capture all emissions. Fire power, fire temperature and thermal efficiency was found not to be affected by the extraction. Sulphur dioxide and Total Suspended Particulates show no significant effect of extraction at a 95% confidence level. A measurable influence of extraction on carbon monoxide emissions was detected, but this was considerably smaller than the effect of the stove. There was no detectable interaction between stove type and extraction level indicating that the influence of the extraction on emissions is independent of the type of stove. It is thus possible to use an extraction hood to compare emissions from different stoves provided the extraction level does not change between tests and falls between the boundaries investigated in this study. The method for setting extraction rates used here is simple and effective and requires no complex measurement techniques. It is feasible that comparisons between emissions from different cooking devices may be made without the aid of air-flow measurements thereby significantly simplifying and reducing the cost of emission assessment in the stove design process.