Air purification is widely promoted to protect patients with allergic airway inflammation; however, evidence supporting its clinical benefits in asthma remains limited. This study aimed to evaluate the effectiveness of portable High-Efficiency Particulate Air (HEPA) H14 air cleaners on indoor air quality (IAQ) and asthma-related health outcomes using a randomized controlled trial design. A total of 100 adults with moderate-to-severe asthma were randomly assigned to either an active HEPA H14 air purifier group or a placebo group and followed for eight months, with assessments at baseline, 4 months, and 8 months. Indoor air pollutants (PM2.5 and PM10) and clinical outcomes, including Asthma Control Test (ACT) score, lung function, rescue inhaler use, and symptom-free days, were analyzed using intention-to-treat analysis. Compared with the placebo group, the active group demonstrated significant improvements in ACT score (β = 2.2, p = 0.004) and symptom-free days (β = 27.7%, P 2.5 levels (-29.6 µg/m³, P < 0.001). These findings indicate that improving IAQ through HEPA H14 filtration provides measurable clinical benefits and serves as an effective complementary intervention for asthma management.
Li et al. (2026) studied this question.