Evaluation of Indoor Pollutant Emission from Portable Air Cleaner
By Hugo Destaillats
Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Indoor Environment Group
Presented in 24th Annual Meeting of the International Society for Exposure Science (ISES), Cincinnati, OH, October 2014.
A wide variety of portable standalone air purifiers are marketed in the US for residential and
commercial use. Various studies have shown that some of these devices, such as electrostatic precipitators, ionizers and ozone generators, can have a negative impact on air quality and public health through emissions of ozone and associated indoor pollutants.
Other air cleaners rely on technologies such as photocatalytic oxidation (PCO), plasma generation and microbial thermal inactivation, for which the impact on indoor air quality has not been fully studied. Some of the latter can potentially generate undesired harmful byproducts, such as fine and ultrafine particles and/or reactive oxygen species (ROS).
We have investigated the primary emissions and secondary reaction byproducts from the operation of six portable air cleaners with a significant market presence in California. Tests were carried out using a 20 m3 room-sized environmental chamber under realistic conditions. Volatile organic compounds (VOCs), ultrafine particulate matter, ozone and ROS were quantified with the air cleaners operating in clean chamber air and in the presence of a challenge VOC mixture. We have also evaluated the removal efficiency for VOCs and particulate matter.
While some devices achieved significant removal efficiencies of some indoor pollutants, others were shown to emit high levels of ozone (up to 3 mg/h) and VOCs as primary emissions (e.g., 85 μg/h toluene) or secondary byproducts (e.g., 16 μg/h formaldehyde and 111 μg/h benzaldehyde). A device emitting high ozone levels also produced a significant amount of ultrafine particulate matter, reaching chamber concentrations of 3x10^3 #/cm3, corresponding to an estimated secondary organic aerosol yield of 1-5 %.
Chamber-derived emission rates are used to predict typical indoor levels, and to evaluate occupant exposures by comparing predicted concentrations with California reference exposure levels and Proposition 65 risk levels.