This is a multi-center randomized, sham-controlled clinical trial to determine the effectiveness of an air cleaner intervention aimed at improving indoor air quality on reducing COPD exacerbation risk and improving quality of life, functional status, rescue medication use.

The Multi-Center Clean Air Randomized Controlled Trial in COPD (Clean Air) is a multi-center, prospective, randomized, double-blind, sham-controlled trial that will enroll 770 former smokers with COPD over a 4-year period and follow participants at regular intervals for one year. The primary endpoint is respiratory specific quality of life. Secondary endpoints include rate of acute exacerbations, rescue medication use, quality of life, and cost-effectiveness.

Inclusion criteria

To be eligible, subjects must meet all these criteria:

1. Age ≥ 40 years.
2. Self-report of physician diagnosis of COPD.
3. Spirometry confirmed airway obstruction (post-bronchodilator spirometry of forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) < 0.7) as defined by the Global Initiative for Obstructive Lung Disease (GOLD) criteria (6, 11)
4. Tobacco exposure ≥ 10 pack-years. This refers to regular cigarette tobacco consumption.
5. Self-reported former smoker of at least 6 months' duration. This does not include e-cigarette use.
6. COPD Assessment Test (CAT) score ≥ 10, Modified Medical Research Council dyspnea scale (mMRC) ≥ 2, or history of moderate or severe exacerbation in the past 12 months (as defined by history of receiving a course of systemic corticosteroids or antibiotics for respiratory problems; or visiting an emergency department or being hospitalized for a COPD exacerbation within the past 12 months.)

Exclusion criteria

To be eligible, subjects must not meet any one of these criteria:

1. Living in a location other than home (e.g., long-term care facility, nursing home)
2. Other chronic lung diseases, except asthma
3. Condition with less than a year of life expectancy (e.g., metastatic cancer) or in hospice
4. Spends >2 months per year in location other than home; or plans to change residence in the next 12 months
5. Pregnant or breastfeeding
6. Current air cleaner use in the home (*If the individual is willing to discontinue use of the personal air cleaner, this person can be eligible if all other eligibility has been met)
7. Inability to bring air cleaners (about 15 pounds each) into home, either by self, friend, or relative
8. Deemed by the study investigator to be unable to complete study protocol, including likely lack of internet connectivity
9. Participating in another interventional clinical trial