Abatement of indoor air pollution achieved with coal–biomass household briquettes

We investigated the abatement of indoor pollution achieved when two types of coal–biomass briquettes (L-BBs and H-BBs) were used in place of honeycombed coal briquettes (H-coal) in household stoves in rural Chongqing, China. Indoor concentrations of sulfur dioxide (SO2), carbon monoxide (CO), and gaseous fluoride were measured. Additionally, we evaluated the factors that affected indoor concentrations of these gases, including the amount of fuel used as well as its sulfur content, the sulfur-emission ratio determined from the amount of sulfur retained in the combustion ash, and the combustion temperature in the stoves. The average 8-h and 24-h SO2 concentrations for L-BBs were nearly equal to or less than the World Health Organization's 40 ppb guideline, whereas those for H-coal and H-BBs exceeded the guideline. The average 8-h SO2 concentrations for L-BBs were from 63 to 89% lower than those for H-coal, even though the 8-h average weight of fuel and its sulfur content for L-BBs were equal to those of H-coal. A chemical analysis of combustion ash indicated that the sulfur-emission ratio was from 26 to 48% for L-BBs, as compared with 86% for H-coal, and this difference resulted in reduction of indoor SO2 concentrations for L-BBs as compared with H-coal. Most of the 8-h average concentrations of CO and gaseous fluoride for all fuels were lower than the WHO guidelines. We concluded that BBs are a useful domestic fuel for the abatement of indoor air pollution.