ICS Magazine

Study concludes portable HEPA filters curb Indoor fungi

November 7, 2001
An ASHRAE study concludes that exposure to airborne indoor fungi in residential environments can be reduced through use of portable high efficiency particulate air (HEPA) filters and regular maintenance of filter material and carpets.

ATLANTA, Ga. -- Exposure to airborne indoor fungi in residential environments can be reduced through use of portable high efficiency particulate air (HEPA) filters and regular maintenance of filter material and carpets, according to researchers at the IAQ 2001 conference.

"Our study showed a 70 percent reduction in airborne indoor fungal levels and a 38 percent reduction in particulate matter in homes fitted with portable HEPA filtration units," C.D. Cheong said. "These results show that the operation of portable HEPA filtration units achieve effective outcomes in reducing levels of airborne indoor fungi. Outdoor sources remain the main contributor to indoor sources of fungi."

Cheong presented a paper, The Use of HEPA Air Filters to Control Airborne Indoor Fungi at the IAQ 2001 conference, Moisture, Microbes and Health Effects: Indoor Air Quality and Moisture in Buildings, sponsored by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The conference was held through Nov. 7 in San Francisco, Calif.

The study involved asthmatic children between the ages of 6 and 11 from schools in Perth, Western Australia. Portable air filtration units fitted with HEPA filters were placed in the children's bedrooms for 15 weeks. Homeowners were told to maintain their normal regular household cleaning practices during the study, including the maintenance (or lack) of the carpets and interior surfaces of the homes.

In addition to the 70 percent reduction in fungal levels and 38 percent of particulate matter, a 53 percent decrease was reported in airborne outdoor fungal levels, Cheong said.

Past studies have indicated the temperature, relative humidity and suspended particulate matter are possible predictors of indoor fungal levels, influencing levels of airborne indoor fungi found indoors. Cheong said this study showed no strong or significant correlations between the air quality parameters and measured indoor fungal levels.

"Use of portable HEPA units, periodic maintenance of both filter material and carpets and a general awareness of indoor air issues like ventilation and source control, could aid in reducing exposure to airborne indoor fungi in residential environments," he said.

The study's authors recommended that future investigations of the efficacy and influence of portable air filters on indoor fungal composition and levels, maintenance of filter material and floor surfaces in the indoor environment should be taken into account.

In addition, issues such as accumulation of dirt, debris and microorganisms in the filter material and resuspension of airborne particulates and microbials from flooring needs to be investigated.

ASHRAE (www.ashrae.org) was founded in 1894. It is an international organization of 55,000 persons. Its sole objective is to advance through research, standards writing, publishing and continuing education the arts and sciences of heating, ventilation, air conditioning and refrigeration to serve the evolving needs of the public.