This project aims to characterize the independent effect of domestic endotoxin exposure on health status, as well as pulmonary and systemic inflammation, in former smokers with COPD. Positive findings from this study would be clinically relevant, as they would provide evidence to support aggressive reduction of ongoing endotoxin exposure in patients with COPD. The investigators also hope to make a methodological advance in the field of endotoxin exposure assessment by elucidating whether settled dust and/or airborne endotoxin measurements are the more relevant exposure of interest in epidemiological studies of respiratory disease. To fulfill the specific aims, the investigators will conduct a longitudinal study, including 75 former smokers with COPD. All subjects will have indoor air monitoring, in-home settled dust collections, home inspections as well as assessments of health status, quality of life (QOL), lung function and pulmonary and systemic inflammation.