HVAC (Heating, Ventilation, and Air Conditioning) filters are designed to capture offensive pollutants in the indoor air of homes and businesses. One of the major contributors to indoor air pollution is mold. Mold spores are easily captured by filters designed for particles of 1.0 microns. This fits within the specifications of a pleated filter with a MERV 6 rating as established by ASHRAE Standard 52.2. As much as 80 percent efficiency can be expected. The higher MERV ratings increase the efficiency.

It is essential for the air to flow continuously through the filter. An air change at six times an hour is recommended for the best removal efficiency. This change rate is significantly reduced during the weeks when temperatures require very little heating or cooling. If the fan is not running, the air is not being cleaned. Some recommend running the fan in a constant "on" position to give continual complete air circulation.

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The MERV rating must be matched with the appropriate hourly air changes for maximum efficiency in removing mold spores from the indoor air. In a commercial setting, a MERV 13 filter is almost 100 percent if the air changes six times every hour. The removal success is hampered if the source of the mold is not addressed. The maximum humidity level in the control of mold should be 50 to 60 percent.

Changing HVAC air filters frequently is important in controlling the mold proliferation. Dirty air filters provide an environment conducive to mold growth and should be replaced or cleaned according to the manufacturer's guidelines. If MERV ratings and ASHRAE guidelines seem too much to remember, look for a MERV rating of 10 or above and most contaminants will be captured.