The Breathe Easy Study utilized a quasi-randomized, within-subjects, parallel-group, pre-post intervention study design with four weeklong periods of indoor air quality (IAQ) and indoor environmental data collection for approximately one year before the installation of mechanical ventilation systems, followed by four weeklong periods of IAQ and indoor environmental data collection for approximately one year after the installation of mechanical ventilation systems, conducted from July 2017 through March 2020 in Chicago, IL. With the nature of a healthy home intervention study by installing residential mechanical ventilation systems within the timeframe, each participant received interventions in the middle of the study period, including continuous exhaust-only systems; intermittent powered central-fan-integrated-supply (CFIS) systems; or continuous balanced systems with an energy recovery ventilator. Thus, each participant served as their own control and there was no formal control group that did not receive intervention nor did they receive a sham/placebo intervention. Primary health outcome, asthma control, was assessed by using the Asthma Control Test (ACT) every month, and quality of life, stress, and other asthma-related health outcomes were assessed via the baseline and end-line surveys.
