Determining what type of air cleaner/purifier to use can be complicated as it depends on what types of indoor air pollutants are to be removed, the size(s) of the indoor space(s), the type of building, and what activities are going on in the building. Budgetary (first cost and maintenance) and energy costs and conservation considerations also must be taken into account. Further, when it comes to some types of air cleaners, marketing claims can be very confusing, the report noted.

For instance, some air cleaners are especially designed to remove particulates only, while others also are fitted to remove gases, vapors, and odors. Some rely on physical mechanisms to capture contaminants and others electrically charge particles to attract them into filters. The filters themselves come in a variety of styles, sizes, and materials, the report said. This past spring, a veritable thunderstorm of controversy erupted in response to a Consumers Report article (May 2006) on another class of air cleaners that produces ozone at high levels for the purpose of air cleaning.

"The idea is ozone reacts with odor-causing VOCs and removes the odor while leaving a fresh, clean smell. Research has shown, however, that ozone as an air cleaner or purifier is not particularly effective and in fact can be hazardous to health. These air cleaners are not to be confused with other electronic air cleaners that produce ozone at very low levels as a byproduct, which are not considered dangerous," Dr. Black said.

One guide to choosing an air cleaner/purifier to is review the results of independent product testing for performance. AQS, for example, offers a comprehensive test method that assesses the effectiveness of air cleaners/purifiers in four distinct areas: