A new PM_2.5-based CADR method to measure air infiltration rate of buildings

Air infiltration is an important way to exchange indoor air with outdoors. It significantly impacts energy consumption and air quality of buildings. Fine particles (PM_2.5) in the outdoor atmosphere environment are a potential natural tracer for the measurement of air infiltration rate, especially in the long term field measurement. In this study, a PM_2.5-based method, named as CADR (clean air delivery rate) method, is developed to supplement traditional tracer gas method in order to make routine measurement in realistic environments possible and convenient. An air cleaner is installed indoors to reduce indoor PM_2.5 concentration. Air infiltration is determined by fitting a model to the decreasing concentration data. Comparison with CO₂ decay method in four different indoor environments gives a normalized mean error of 19% and a correlation coefficient of 0.80 for this method. This justifies the CADR method as a feasible option to measure air infiltration rate. Although subject to several constraints, the proposed method would facilitate field measurement under realistic conditions by being combined with current tracer gas methods.