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

• Published in: Building and environment 2021-12, Vol.206, p.108325, Article 108325
• Main Authors: Das, Darpan, Moynihan, Emma, Nicas, Mark, McCollum, Eric D., Ahmed, Salahuddin, Roy, Arunangshu D., Chowdhury, Nabidul, Hanif, Abu A.M., Babik, Kelsey R., Baqui, Abdullah H., Ramachandran, Gurumurthy
• Format: Article
• Language: English
• Subjects: Air changes per hour; Air pollution; Biomass burning; Cookstove; Decay; Decay rate; Exposure; Exposure modeling; Far fields; Households; Indoor air pollution; Kitchens; Particulate emissions; Particulate matter; Pollutants; Rural areas; Rural households; Solid fuels; Ventilation
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2021.108325

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 over-estimate based on using an incorrect model to derive the ACH values. •Previous cookstove studies have estimated the air changes per hour (ACH) to be ~ >20.•Obtaining the ACH from the decay curve of concentrations in the vicinity of the pollutant source leads to over-estimates.•A two-compartment model provided more realistic ACH values.•We recommend that a two-compartment model be used for the determination of ACH values.•The revised methodology can be used by WHO to develop more appropriate emission targets for cookstoves