Elevated levels of outdoor particulate matter (PM) have been associated with increased rates of morbidity and mortality. This has led to the development of air quality guidelines and standards from organizations such as the World Heath Organization (WHO) and the United States Environmental Protection Agency (EPA). Though epidemiological studies focus on outdoor PM, people spend the majority of their time indoors. Air filters in the HVAC system act to remove airborne particles from both indoor and outdoor sources and to lower occupant exposure. ASHRAE 62.1-2010 sets forth the required Minimum Efficiency Reporting Value (MERV) for filter installations in North America. Standard practice is to select MERV rating according to ASHRAE guidelines without regard to ambient PM concentrations.

The purpose of this study is to investigate the effect of varying the efficiency of filter installations on indoor aerosol concentration. A standard indoor particle dynamics model was used to determine indoor aerosol concentrations based on annual average outdoor PM in a number of cities. The cost of operating filtration systems with varying MERV ratings was determined and compared with the benefits of reduced indoor particle concentrations. The minimum filtration efficiency and average power requirement to meet EPA air quality guidelines was determined for a number of major cities worldwide. The results from this work highlight the potential reduction in energy consumption for building operation when selecting filtration systems to meet desired indoor air quality rather than installing filters prescribed to achieve points in a building rating scheme.