Multi-Center Clean Air Randomized Controlled Trial in COPD

This randomized controlled trial is testing whether using high-quality air purifiers at home reduces breathing problems and flare-ups in people with COPD (a chronic lung disease often caused by smoking). **You may be eligible if...** - You are 40 years or older - You have a doctor's diagnosis of COPD confirmed by breathing tests - You have a smoking history of at least 10 pack-years (e.g., 1 pack per day for 10 years) - You are a former smoker who quit at least 6 months ago - You have significant COPD symptoms or had a moderate-to-severe flare-up in the past year **You may NOT be eligible if...** - You are still smoking - You do not have confirmed COPD on lung function testing - You have not had significant COPD symptoms or exacerbations - You have other conditions that would prevent safe participation Talk to your doctor to see if this trial is right for you.