The investigators will conduct a randomized, controlled, double-blind, crossover trial to determine whether the presence of a portable high-efficiency indoor air filter in the bedroom reduces respiratory symptoms in former smokers compared with placebo. The primary outcomes will be change in St. George's Respiratory Questionnaire - COPD (SGRQ-C) score associated with using a portable high-efficiency indoor air filter during the study period. Secondary outcomes of COPD exacerbations and hospitalizations, daily step counts, medication changes, spirometry, and cardiovascular outcomes will also be assessed.