The burden of childhood asthma is borne disproportionately by children living in poverty and in urban centers, many of whom are from communities of color and are at greater risk for environmental exposures. Given the complex interaction of physical and social environmental factors on childhood asthma, there have been increasing calls for comprehensive efforts using a community-based participatory research (CBPR) approach. Community Action Against Asthma is a long standing CBPR partnership in Detroit, Michigan, composed of representatives from community-based organizations, health and human service agencies, and academia. All members of the partnership have been actively involved in the development of the CBPR project proposed here. The specific aims are: 1) to test the efficacy of air filters (AFs) separately and when combined with air conditioners (ACs) to reduce exposure to particulate matter (PM), over and above a standard community health worker home visit (standard) intervention; 2) to test the association between any reduction in PM exposure through the use of AFs separately and when combined with ACs over and above a standard intervention and health outcomes in children with asthma; 3) to elucidate the causal pathways by which any intervention-related improvements in children's asthma-related health status is occurring. One hundred and fifty households in Detroit, Michigan with at least one child with mild persistent or moderate to severe persistent asthma will be enrolled to participate in the study. Households will be randomly assigned to one of three groups: a standard household intervention (or control) group; an AF only intervention group; or an AF+AC intervention group. Extensive health and exposure measures will be undertaken during the course of the 12 -month intervention. Given the role of PM in children's asthma-related health and the higher concentrations of PM in microenvironments, there is a need to test the efficacy and efficiency of novel approaches to reducing indoor air pollutants. Doing so using a CBPR approach will enhance the relevance and ultimately the success of this proposed research.