VC-21A-C030 - Testing of Granular Air Cleaning Media for Ozone Removal inASHRAE Standard 145.1 Setup

Ozone is one of the important air contaminants due to its adverse health effects including respiratory irritation, eye irritation and lung damage. It forms through a series of reactions involving volatile organic compounds and nitrogen dioxide in the presence of sunlight and introduces to the indoor environment by natural or mechanical ventilation. Additionally, devices such as photocopiers, laser printers, and some air cleaners generate ozone in the indoor environment. Therefore, using an ozone removal media, such as activated carbon, is crucial to protect the occupants’ health. ASHRAE standard 145.1—a laboratory test method—assesses the loose granular media’s performance for the removal of various gaseous air contaminants, including ozone. According to this standard, the test conditions for ozone removal media are 1 ft3.min-1 (0.0282 m3.min-1) flow rate, 50% relative humidity, 73.4 °F (23 °C) temperature, 0.1 s residence time, 0.00176 ft3 (0.00005 m3) media loading, and 1 ppm ozone concentration. In this paper, we tested different granular activated carbons, including coal-based, impregnated coal-based, coconut shell-based, and palm shell-based, as well as catalysts specifically designed for ozone removal. We ran the tests according to the ASHRAE 145.1 standard test method condition at 2 concentration levels; 1 ppm as specified in the standard and 50 ppm. Also, we studied the effect of granular size on the ozone removal performance. The coconut shell-based activated carbons have the best performance (>99% efficiency after 6 h exposure to 50 ppm ozone) while the coal-based ones have the poorest (56% after 6 h exposure to 50 ppm ozone). However, impregnating the coal-based activated carbon with KOH improves its efficiency significantly; 64% improvement. It was not feasible to reach the 50% breakthrough—the test method requirement—in a one-day test. Besides, we could not see any considerable difference in the performance of different materials after 6 h exposure to 1ppm ozone. This indicates that the ASHRAE standard 145.1 is not viable as a ranking test. Also, it cannot provide sufficient data to predict the media service life unless one continues the test for an extremely long period. Therefore, the purpose of the standard 145.1 is not fully fulfilled for ozone removal testing.