Beyond Ozone: Cleaning Outdoor Air for Improved IAQ

Outdoor ozone is a major concern and there have been concerted efforts to reduce its concentration. However, data has shown an increase in tropospheric ozone levels of between 1 and 2% per year over the last 30 years. As of April 2009, the United States Environmental Protection Agency indicates more than 40% of the population live or work in areas exceeding the current federal standard for ozone. Other countries are also experiencing problems with ozone such that in many locations it is the primary reason for air quality alerts being issued. Ground-level ozone also negatively impacts the indoor environment and in addition to the direct exposure to ozone, there is also the potential for exposure to ozone reaction products; some of which are known to adversely affect human health. Control of ozone is now required by some building standards. Air cleaning for ozone typically involves the use of granular dry-scrubbing air filtration media and studies have shown that even when the media is effectively spent with regards to other chemical contaminants, ozone removal efficiency can still be above 50%. However, air cleaners for ozone are used in only a small minority of buildings due to a lack of strong and enforceable standards for cleaning outdoor air and a general lack of perceived benefits in doing so. Still, considerable effort is being devoted to new product development and has resulted in a combination filter that can control both particulate contaminants and along with ozone. Using this type of filter, a properly designed, installed, and maintained air cleaning system will be able to remove significantly more than just ozone. Estimates of the incremental annual cost for ozone air cleaning are in the range of US$0.04 - 0.10 per ft(2) per year. This paper will discuss ozone in ambient (outdoor) air, its effects on human health and well-being, current air quality standards and guidelines, and provide practical examples of how air cleaning is being used to effectively control ozone and improve IAQ.