To guide the selection and design of air filter/cleaning devices for improving indoor air quality, it is important to understand assess the performance and characteristics of filter media within a reasonable and practical testing period. To provide comparable and objective data for designers and users of gas phase filtration equipment and HVAC systems, the long-term experimental data of filter media at typical low levels of indoor pollutant concentration (~50 ppb) are desirable but they are time-demanding and experimentally expensive to obtain via testing. The current standard testing per ASHRAE 145.1-2008 is performed at relatively high levels of challenge concentrations (~1-100 ppm), which calls for a systematic approach to correlate high concentration testing results with the performance of filters at indoor low concentration.