Air pollution is one of the most serious threats to human well-being globally and especially in urban South Asia. As air pollution levels remain high in many cities, it is important to understand what defensive investments households can make in order to reduce the damage caused by air pollution. Indoor air purifiers are one of the most widely used and promising private defensive investments to reduce air pollution’s negative impacts. However, evidence of their effects is limited and usage remains low in low- and middle-income countries where air pollution is the highest. We propose to conduct an RCT on air purifiers in households in Dhaka, Bangladesh. The project has three main objectives. First, to understand how different framings of the air pollution problem lead to different levels of interest in taking action to protect oneself and one’s family. Second, to understand the current willingness to pay for air purifiers, how it can be brought closer to market prices,as well as what determines the usage among those owning an air purifier. Third, to estimate the effects of air purifiers on health, labor supply, income, and cognition.