Although biomass fuels are cheap and easily available, they are inefficient not only because they are low warming but also because they produce many pollutant products. For example, wood smoke is a complex mixture of numerous volatile and particulate substances derived from wood polymers and resins. More than 200 chemical and compound groups have been identified, and > 90% of these are in the inhalable size range.6,7 A significant number of these biomass smoke constituents are known to be toxic or have irritant effects on the respiratory tract and include particulate matter that are < 10 microns in aerodynamic diameter (PM10), carbon monoxide (CO), nitrogen dioxide, sulfur dioxide, aldehydes (eg, formaldehyde), polycyclic aromatic hydrocarbons (eg, benzopyrene), volatile organic compounds, chlorinated dioxins, and free radicals. Among these, PM10 has the most significant adverse health impacts. In homes that use biomass fuels, the mean 24-h PM10 levels have been shown to reach 300 to 3,000 μg/m3 and sometimes can be as high as 30,000 μg/m3.1 Daytime respirable particulate measurements in homes using biomass fuel in China, Kenya, Mexico, Guatemala, Brazil, and India show average PM10 levels of ~ 1,000 μg/m3 but easily reach levels up to 3,000 μg/m3.8 The US Environmental Protection Agency (EPA) safety standard for 24-h average PM10 exposure is 150 μg/m3. The levels encountered in homes that use biomass fuel are therefore ~ 10 to 70 times above ambient levels observed in some of the most polluted cities of the world. Moreover, the mean CO concentrations in homes that use biomass fuel are typically in the range of 2 to 50 ppm but can be as high as 500 ppm during cooking,9 which is significantly greater than the EPA 8-h safety standard for CO (< 9 ppm).