Indoor concentrations of nitrogen dioxide and sulfur dioxide from burning solid fuels for cooking and heating in Yunnan Province,China

The Chinese national pollution census has indicated that the domestic burning of solid fuels is an important contributor to nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) emissions in China. To characterize indoor NO₂ and SO₂ air concentrations in relation to solid fuel use and stove ventilation in the rural counties of Xuanwei and Fuyuan, in Yunnan Province, China, which have among the highest lung cancer rates in the nation, a total of 163 participants in 30 selected villages were enrolled. Indoor 24‐h NO₂ and SO₂ samples were collected in each household over two consecutive days. Compared to smoky coal, smokeless coal use was associated with higher NO₂ concentrations [geometric mean (GM) = 132 μg/m³ for smokeless coal and 111 μg/m³ for smoky coal, P = 0.065] and SO₂ [limit of detection = 24 μg/m³; percentage detected (%Detect) = 86% for smokeless coal and 40% for smoky coal, P < 0.001]. Among smoky coal users, significant variation of NO₂ and SO₂ air concentrations was observed across different stove designs and smoky coal sources in both counties. Model construction indicated that the measurements of both pollutants were influenced by stove design. This exposure assessment study has identified high levels of NO₂ and SO₂ as a result of burning solid fuels for cooking and heating.     

Experimental investigation of the air flow and indoor carbon dioxide concentration in classrooms with intermittent natural ventilation

Air flow and the associated indoor carbon dioxide concentrations have been extensively monitored in 62 classrooms of 27 naturally ventilated schools in Athens, Greece. The specific ventilation patterns as well as the associated carbon dioxide concentrations, before, during and after the teaching period are analysed in detail. During the teaching period, only 23% of the measured classrooms presented a flow rate higher than the recommended value of 8 l/p/s while the mean daily fluctuation was close to 40%. About, 52% of the classrooms presented a mean indoor CO₂ concentration higher than 1000 ppm. The specific experimental data have been compared against existing ventilation rates and carbon dioxide concentrations using published information from 287 classrooms of 182 naturally ventilated schools and 900 classrooms from 220 mechanically ventilated schools. The relation between the air flow rates and the corresponding indoor carbon dioxide is analysed and then compared to the existing data from naturally and mechanically ventilated schools. It is found that all three data sets present a CO₂ concentration equal to 1000 ppm for air flows around 8 l/p/s. Specific adaptive actions to improve the indoor environmental quality have been recorded and the impact of indoor and ambient temperatures as well as of the carbon dioxide concentration on window opening is analysed in detail. A clear relation is found, between the indoor temperature at which the adapting action takes place and the resulting air flow rate. In parallel, a statistically significant relation between window opening and the indoor–outdoor temperature difference has been established.