For the proposed study we will conduct a randomized controlled trial (RCT) comparing a standard community health worker home visit intervention (the standard intervention) to an Air Filter(AF) only intervention that adds the use of an AF in the child's bedroom to the standard intervention (AF only intervention) and an Air Filter(AF)+ Air Conditioner (AC) intervention that adds the use of an AF and AC in the child's bedroom to the standard intervention (AF+AC intervention) (Figure 1). We will test whether the addition of AFs (and, in the warmer months, ACs) to the standard intervention, as compared to the standard intervention will: (1) further lower children's exposure to PM (Specific Aims 1a, 1b), and (2) further improve asthma-related health status of children (Aims 2a, 2b). One hundred and fifty Detroit households with at least one child aged 6 to 12 with symptoms consistent with persistent asthma (mild, moderate, or severe) will be enrolled in the study . Following collection of baseline data, households will be randomly assigned to receive one of three interventions: the standard household intervention, the AF only intervention, or the AF+AC intervention. Participants assigned to the AF only intervention group will receive AFs at the start of the 12-month intervention (Summer/Fall 2008). Those assigned to the AF+AC intervention group will receive AFs at the start of the intervention period but ACs will not be in place during the first summer of the intervention, but will be installed in June 2009 prior to the second summer of the intervention (Figure 2). Data will be collected across all seasons (Fall 2008 through Winter 2009) which will enable us to evaluate directly the exposure and health outcome effects (Specific Aims 1a and 2a, respectively) of the addition of AFs alone to the standard intervention as well as the exposure and health outcome effects of the AFs augmented by ACs (Aims 1b, 2b). This design will also allow for comparisons, adjusted for any changes in the exposure and health status of the intervention groups, of the combined effect of the AC and AF to that of the AF alone.