Household air pollution (HAP) from biomass fuel burning is linked to poor health outcomes. Improved biomass cookstoves (ICS) have the potential to improve HAP.

A pre-/post- intervention study assessed the impact of six ICS on indoor air quality and acceptability of ICS to local users in rural Western Kenya.

We measured mean personal and kitchen level concentrations of particulate matter <2.5μm in diameter (PM_2.5, μg/m³) and carbon monoxide (CO, ppm) during the 48-hour period of each ICS use in 45 households. We compared these levels to those observed with traditional 3-stone fire (TSF) use. We assessed ICS acceptability through interviews and focus groups. We evaluated association of stove type, fuel use, and factors related to cooking practices with mean kitchen PM_2.5 and CO using multivariable regression.

Stove type, exclusive ICS use (vs. concurrent TSF use), and the amount of fuel used were independently associated with kitchen PM_2.5 and CO levels. Reductions (95%CI) in mean PM_2.5 compared to TSF, ranged by ICS from 11.9% (-2.8–24.5) to 42.3% (32.3–50.8). Reductions in kitchen CO compared to TSF, ranged by ICS from -5.8% (-21.9–8.2) to 34.5% (23.2–44.1). Mean kitchen PM_2.5 ranged from 319μg/m³ to 518μg/m³ by ICS. Women thought ICS were easy to use, more efficient, produced less smoke, and cooked faster, compared to TSF. Women also reported limitations for each ICS.

We documented reductions in HAP from ICS compared to TSF. The PM_2.5 levels with ICS use were still considerably higher than WHO indoor air quality guidelines. Achieving maximal potential of ICS requires adherence to more exclusive use and addressing user reported ICS limitations.