Participants in the intervention arm will receive sham air purifiers, which will be installed in their bedroom and the room where they spend the most time at home. The devices will operate continuously for the entire intervention period.

The COPD Assessment Test (CAT) is a questionnaire for people with COPD. It is designed to measure the impact of COPD on a person's life and how this changes over time. The total score ranges from 0 to 40, with higher scores indicating a more severe impact of the disease on the patient's life.

Physician diagnosed exacerbation of acute COPD

Measured by quantitative CT (QCT) analysis software on inspiratory chest CT. The absolute thickness of the airway wall (mm) is measured from the inner to the outer lumen boundary.

The luminal area (mm²) of the pre-specified segmental and sub-segmental bronchi will be measured using quantitative CT analysis software.

The pulmonary function measures are performed by a professional medical device. Before the pulmonary function test, subjects practice several times with the guidance of professional staff. During the examination, each subject is in a sitting position and clamps the nose clip, and repeats the test, with the best result as the criterion.

The pulmonary function measures are performed by a professional medical device. Before the pulmonary function test, subjects practice several times with the guidance of professional staff. During the examination, each subject is in a sitting position and clamps the nose clip, and repeats the test, with the best result as the criterion.

The pulmonary function measures are performed by a professional medical device. Before the pulmonary function test, subjects practice several times with the guidance of professional staff. During the examination, each subject is in a sitting position and clamps the nose clip, and repeats the test, with the best result as the criterion

The pulmonary function measures are performed by a professional medical device. Before the pulmonary function test, subjects practice several times with the guidance of professional staff. During the examination, each subject is in a sitting position and clamps the nose clip, and repeats the test, with the best result as the criterion.

The pulmonary function measures are performed by a professional medical device. Before the pulmonary function test, subjects practice several times with the guidance of professional staff. During the examination, each subject is in a sitting position and clamps the nose clip, and repeats the test, with the best result as the criterion.

The pulmonary function measures are performed by a professional medical device. Before the pulmonary function test, subjects practice several times with the guidance of professional staff. During the examination, each subject is in a sitting position and clamps the nose clip, and repeats the test, with the best result as the criterion.

The respiratory impedance measures are performed by a professional impulse oscillometry (IOS) device. During the examination, each subject is in a sitting position, wears a nose clip, and is instructed to maintain normal tidal breathing. Professional staff guide the subjects to support their cheeks with both hands to prevent upper airway shunting.

The respiratory impedance measures are performed by a professional impulse oscillometry (IOS) device. During the examination, each subject is in a sitting position, wears a nose clip, and is instructed to maintain normal tidal breathing. Professional staff guide the subjects to support their cheeks with both hands to prevent upper airway shunting.

A NIOX VERO Sensor is used to measure fractional exhaled nitric oxide (FeNO), a biomarker of airway inflammation. After deep breathing, the subjects gently inhaled into the device. The instrument shows the subjects' FeNO levels.

Detect the absolute count of eosinophils in peripheral blood samples to evaluate the potential response to air purification.

Measure the concentration of neutrophils in blood samples to evaluate the potential response to air purification.

Detect the concentration and expression levels of systemic proteins in blood samples to examine the differential protein signatures between the intervention and control groups.

Measure the concentrations of total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) in blood samples to evaluate the potential metabolic response to air purification, particularly regarding cardiovascular risk.

Measure fasting plasma glucose levels in blood samples to assess the potential impact of air purification on acute glucose metabolism.

Measure skeletal muscle mass using bioelectrical impedance analysis to evaluate the potential effect of air purification on muscle preservation in COPD patients.

Measure body fat percentage using bioelectrical impedance analysis to assess the potential impact of air purification on adiposity.

AHI is a polysomnography-derived measure of sleep-disordered breathing severity, calculated as the total number of apnea and hypopnea events per hour of sleep. Higher AHI values indicate more severe sleep-disordered breathing.

Measured nightly by a contactless ballistocardiography (BCG) sensor mat under the pillow to determine the time (minutes) from lights off to the first sleep epoch.

Measured nightly by a contactless ballistocardiography (BCG) sensor mat under the pillow, summing all sleep epochs (minutes) from sleep onset to final awakening to assess the potential impact of air purification on sleep quantity.

Calculated from inter-beat intervals (J-J intervals) extracted from BCG signals recorded by the under-pillow mat; reported as root mean square of successive differences (ms) to assess the potential impact of air purification on autonomic nervous system function.

MACE is defined as a composite endpoint including: ischemic heart disease/coronary artery disease (I20, I24, I25), myocardial infarction (I21, I22, I23), atrial fibrillation (I48), venous thromboembolism (I74, I80, I82), heart failure (I50), and stroke (I60, I61, I62, I63, I64, I69). Events will be identified through medical records and follow-up assessments.

Measure the maximum grip strength (in kilograms) using a hand dynamometer to evaluate the potential effect of air purification on muscle strength and functional status in COPD patients.

Measure systolic and diastolic blood pressure (in mmHg) using a validated electronic sphygmomanometer to evaluate the potential effect of air purification on hemodynamic function.