We humans spend most of our time indoors, and most of that time in residences, where we are exposed to airborne particulate matter that can lead to a wide range of mild to serious adverse health effects. Air filtering with continuous Heating, Ventilation, and Air-Conditioning (HVAC) fan operation or room air cleaners can reduce human exposure to airborne pathogens and other particulates. In addition to filtering, HVAC fan operation mixes the air, breaking up localized high contaminant concentrations. Air mixing and elevated airspeeds from HVAC fan operation also aid thermal comfort. Due to its lower airflow than an HVAC fan and confinement in the lower part of the room, a portable air cleaner has limited mixing effect. Ceiling fans are commonly used to mix air for thermal comfort at higher temperature set points. Modern ceiling fans and room air cleaners typically use much less energy than a typical HVAC fan, and because they can be turned on only in occupied spaces, they likely have an energy conservation advantage over continuous HVAC fan operation. An alternative to continuous HVAC fan operation is a combination of room air cleaners and ceiling fans for (i) filtering, (ii) mixing, and (iii) thermal comfort associated air movement.

This study compares combinations of ceiling fans and air cleaners with continuous HVAC fan operation in residential environment for air quality, thermal comfort, and energy use. This study shows how to normalize data across experiments to compare HVAC filtration and various combinations of ceiling fans and room air cleaners from one test to another. One combination of ceiling fans and a portable air cleaner was slightly more effective and much more energy efficient than continuous HVAC operation for ultrafine particle removal, but continuous HVAC operation outperformed the portable air cleaner in all configurations for particles in the 1-2.5 µm and 2.5-5 µm size ranges. This study points the way to further testing to explore air cleaner and ceiling fan combinations that could be more effective and energy efficient than HVAC operation across all particle sizes of concern.