Estimating residential air exchange rates in rural Bangladesh using a near field-far field model

摘要

Household air pollution due to solid fuel (biomass) combustion is widely prevalent in rural households in the developing world. Providing adequate ventilation can be a potential method to reduce exposures to residents. Previous cookstove studies in rural areas around the world have estimated the ventilation air changes per hour (ACH) values to be of the order of 20. These studies use a one-compartment model to estimate the ACH from the decay of the pollutant released very near to the cookstove. While the one-box compartmental model is appropriate for estimating exposures farther away from emission sources, a multi-compartment (e.g., a 2-box model) may be more appropriate for distinguishing between exposures of the cook versus other occupants in the house, as well as estimating ventilation rates in the house. In the present study, we use a two-compartment model to estimate the ACH. Field based particulate matter measurements were carried out in 40 Bangladesh rural households in kitchen and living room. The overall Geometric Mean (Geometric Standard Deviation) of ACH across households were found to be 0.43 (4.3) in the kitchen and 0.32 (2.7) in the living room. Obtaining the air changes per hour or ventilation rates from the decay curve of concentrations in the near vicinity of the pollutant source will lead to significant over-estimates. Our findings indicate that there is currently a substantial overestimate based on using an incorrect model to derive the ACH values.