Molds are tiny fungi that reproduce by proliferation of spores ranging in size from 1 to 100 microns. Molds can grow anywhere when water is present.

Here is one of the most common problems I find in consumer air purifier reviews: someone has installed an air purifier to "get rid of mold." Some complain that high priced HEPA purification has failed to remove the musty odor. Others gleefully report that the air smells "fresh" after using an ozone making "air purifier."

This is the key to ozone's success as an air purifier: active purification. It hangs about for days, oxidizing biologicals like mold. Unfortunately, ozone levels high enough to remove mold are unsafe for anyone, especially those with any illness.

In some cases, shock ozone treatments can be the best solution to a mold problem. But only where people and pets are out of the home. This is a good job for professionals. Ozone emitting air purifiers are not recommended for daily use.

The key to understanding mold is moisture. Mold will grow on a wide range of materials, when water is present. When mold grows unchecked indoors, it produces millions of airborne spores. Indoor mold spore counts can be many times higher than outdoors. These concentrations are hazardous to everyone, allergic or otherwise.

If you have a mold situation, investigate the source of moisture. Wet basements are a common source, sometimes impossible to cure. Air conditioning (HVAC) coils, collectors, and pans are often hidden sources.

If there is leaking plumbing, roofing, or a downspout that dumps runoff near the house, there may be mold. Installing an air purifier for allergy to mold under damp conditions is bound to be a disappointment.

Water damage that has resulted in significant mold growth could require remediation by a licensed contractor. Replace rotted or damp organic building materials; wood, ceiling tile, carpeting, wallboard, and wallpaper. Particleboard kitchen and bath countertops, with pressed wood hiding under a thin facade of Formica plastic venire are often moldy on the underside.

Ionizers are not very effective at lowering mold counts. UV light can reduce mold, but the application to large areas is problematic.

UV light intensity, which decreases rapidly with distance from the bulb, must dose the mold for a time measured in minutes. Air purifiers with uv tend to use it on the filters or to activate photocatalysts. The best application of uv in a mold allergy situation is for disinfecting air conditioning coils and evaporation pans.

Newer air purification technologies are arriving that will surpass ozone for normal household mold remediation. These are hydroxyl radical oxidizers, safer with their short lives, and photocatalytic oxidizers, which burn microorganisms with high tech semiconductors. Sharp FPN60CX would be a good alternative to ozone for a mold situation, but only for a limited room size, say under 200 square feet. The portable Sharps could easily be moved to the mold source, i.e. kitchen or bath.

Photocatalytic air purification, without paper filters, thrives in damp environments. A new and inexpensive model, the Nanobreeze, would do well in localized damp areas like baths and kitchens.

Control moisture with source removal and dehumidifiers.

When moisture is gone, properly sized HEPA air purifiers are effective at purifying airborne mold. Dedicated air sterilizers, such as Airfree and Eco-rx can help after the moisture is removed.