ARB Research Seminar

This page updated October 9, 2014

Evaluation of Pollutant Emissions from Portable Air Cleaners

Photo of Hugo Destaillats, Ph.D

Hugo Destaillats, Ph.D., Deputy Leader, Indoor Environment Group, Lawrence Berkeley National Laboratory

November 04, 2014
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Introduction
Presentation
Video
Research Project
Interview

Overview

A wide variety of portable standalone air purifiers are sold for residential and commercial use. This presentation will describe a study of air cleaners relying on emerging technologies that include photocatalytic oxidation, plasma generation and microbial thermal inactivation. Poorly engineered devices may negatively impact indoor air quality (IAQ) through emissions of ozone, volatile organic compounds (VOCs), particulate matter and/or reactive oxygen species (ROS).

The objective of this study was to evaluate the primary and secondary emissions of air pollutants from six devices commercialized as portable air cleaners in California. Tests were carried out using a 20-m³ room-sized environmental chamber under realistic indoor conditions. Pollutant levels were first determined when the air cleaners were operated in clean chamber air, and then in the presence of a challenge VOC mixture that simulated conditions commonly found in homes. The removal efficiencies for VOCs and particles were also evaluated. Four of the devices removed between 8% and 29% of VOCs at rates between 600 and 1700 μg h⁻¹, while two others actually emitted VOCs at rates of 300 - 1400 μg h⁻¹. Both primary VOC emissions (e.g., 85 μg h⁻¹ toluene) and formation of secondary oxidation byproducts (e.g., 16 μg h⁻¹ formaldehyde) were observed. Good particle removal efficiency was observed in two devices, which reduced the ultrafine particulate (UFP) number concentration by 35% to 90%. One device emitted very high ozone levels (up to 6 mg h⁻¹) and, in the presence of the challenge VOC mixture, also produced UFP reaching concentrations of 3 x 10³ particles per cm³ consistent with an estimated secondary organic aerosol yield of 1-5%. Sampling and analytical methods were developed to determine ROS concentrations. The plasma device produced above-background ROS levels, with equivalent hydrogen peroxide concentrations in the order of 0.5 ppb.

Chamber-derived emission rates were used to model typical indoor levels and to assess occupant exposure by comparing predicted levels to California health-based standards. Results indicated that most emitted VOCs were below health-based exposure standards, but in one modeling scenario, hazardous levels were exceeded for ozone, formaldehyde, and benzene. These findings will help the Air Resources Board assist the public in making informed decisions when purchasing and using portable air cleaners, and to identify which health and IAQ concerns associated with these technologies need to be further addressed. These results, along with those from other studies, can also contribute to the development of effective standard testing procedures, which are needed to control potentially harmful emissions and verify the soundness of marketing claims. In addition, these findings may help manufacturers develop the appropriate engineering controls needed to prevent harmful contaminants from being released indoors.

Speaker Biography

Hugo Destaillats, Ph.D., is a Staff Scientist and Deputy Leader of the Indoor Environment Group at the Lawrence Berkeley National Laboratory. Prior to joining LBNL in 2003, he was a postdoctoral researcher at the California Institute of Technology (1998-2001) and at the University of California, Davis (2001-2003). Dr. Destaillats' research over the past 16 years has been in the fields of environmental, physical and analytical chemistry. Current efforts are aimed at understanding the sources, transport and elimination of indoor trace pollutants, preventing or mitigating human exposures to harmful chemicals, and developing new technologies and materials for healthy and energy-efficient built environments. Dr. Destaillats has published more than 50 articles in peer-reviewed journals, and holds a Ph.D. in Chemistry from the University of Buenos Aires, Argentina.


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