Asthma Intervention with Residential Ventilation and Air Cleaner (AIRVAC) Study: A 4-arm parallel-group randomized controlled trial protocol

Background: Evidence linking exposure to airborne particulate and gaseous pollutants, as well as mold spores, with asthma control and severity is well established. A growing body of literature has demonstrated that ventilation and air filtration can improve indoor air quality (IAQ); however, clinical evidence on their comparative health impacts remains limited. Therefore, this trial aims to evaluate the long-term effectiveness of energy recovery ventilators (ERVs) and portable air cleaners (PACs) in reducing indoor air pollutants and mold levels and improving health outcomes in individuals with asthma. Secondary objectives includes associations between housing conditions, occupant behaviors, indoor environmental exposures, and asthma-related health outcomes. Methods: The AIRVAC study is a single-blind, placebo-controlled, 4-arm, parallel-group, randomized controlled trial, with a pre-intervention period of up to 1 year and a 1-year post-intervention period. Children aged 5–17 years and adults with physician-diagnosed asthma will be recruited from more than 80 households across the Dallas-Fort Worth (DFW) area in Texas. Following the pre-intervention period, each household will be randomized to receive one of four different interventions midway through the study: (1) active ERVs, (2) sham ERVs, (3) active PACs, and (4) sham PACs. Primary health outcomes include asthma control; secondary outcomes include pulmonary function, asthma-related quality of life, stress, and sleep quality. Initial housing assessments will be conducted prior to the pre-intervention period to characterize occupant behaviors and housing-related factors that may contribute to asthma exacerbations and affect ERV installation. Environmental exposures will be assessed by combining measurements of indoor and outdoor air pollutants, including particulate matter (PM), nitrogen dioxide (NO2), carbon monoxide (CO), and volatile organic compounds (VOCs), as well as temperature, relative humidity, and indoor and outdoor mold, using low-cost and research-grade air quality sensors and mold sampling methods. Discussion: Findings from the AIRVAC study will provide important evidence on the comparative effects of residential ventilation and air cleaning interventions on IAQ, mold, and asthma-related health outcomes among children and adults with asthma. The study will also examine the relationships among housing characteristics, occupant behaviors, indoor environmental exposures, and asthma-related health outcomes, while providing insights into the operation and performance of residential ventilation and air cleaning interventions in vulnerable households.