The investigators seek to determine the effect of placing air cleaner devices in the homes of adults with asthma on the adults' asthma health. To this end, the investigators aim to study 40 adults with asthma that are 18-50 years of age and live in Baltimore. Participants will receive either true air cleaners or sham cleaners in a blinded, randomized manner for one month, and then, after a washout period, participants will cross over and receive the other intervention (sham or true cleaner). All participants will have environmental monitoring (personal and in-home) to determine participants' particulate matter exposure, and be followed repeatedly during the 3 month study period for markers of asthma disease, including respiratory symptoms, medication and health care utilization, pulmonary function, systemic markers of inflammation, and bronchoscopic evidence of airway inflammation or epithelial cell dysfunction.
