Carpet Cleaning and Mold Growth

Carpet cleaning and mold growth: it’s a fine line!

Wet carpeting is an ideal mold breeding ground if it is not immediately dried. Carpet dries quickly if there is a low relative humidity air around it — and vice versa. If the air around it has high relative humidity, it does not dry. Within 24–48 hours mold spores become active.

According to the EPA, “the key to mold control is moisture control.” Any wet-process carpet cleaning will always leave enough moisture in the carpet to grow mold. An effective drying process is necessary.

Effective drying can be accomplished in various ways:

“Natural” Drying: If the outside air is warm and dry, open the windows. Moisture equalizes quite readily.

Adding Heat: If the outside air is cold (below 50°F), ventilating and heating the air quickly dries the carpet.

Proper Use of A/C: If it’s hot, the A/C unit cools the air and removes some water. When the A/C shuts off (because the temperature is satisfied), an increase in heat must trigger the A/C to operate again. If the A/C unit is constantly providing low RH to the space, the carpet will dry. CAUTION — Improper use of the A/C can create ideal conditions for mold growth!

Dehumidifiers: Dehumidifiers are a sure-fire way to provide the dry air necessary to guarantee carpet drying.

In each case, fans will speed up the drying process.

*Simply lowering the thermostat to make the A/C operate can actually create condensation and increase moisture. For example, if the dew point of the outdoor air is 70°F, cooling surfaces below 70°F will cause condensation. To avoid this problem of “over-cooling”, an A/C unit requires ‘reheat’.


Therma-Stor manufactures a complete line of dehumidifiers including ducted and portable units. The portable units most commonly used for carpet drying or water damage emergencies are as follows:

The Phoenix 250 MAX is the powerful, rugged portable unit ideal for drying after carpet cleaning and/or other water damage. It’s the most powerful unit (145 pints/day) that plugs into a standard 115-volt outlet (8.2 amps) and still allows air movers on the same circuit. It has built-in shock absorbers and offers high efficiency air filtration.

The Santa Fe Rx is a powerful, self-contained, portable unit designed specifically to be quiet. Wheel it in, run the hose to a drain (from the built-in condensate pump), and set the dehumidistat. The Santa Fe Rx is Energy Star® rated as the most efficient unit in the industry — using only 5.4 amps to remove over 74 pints of water per day! It typically handles 2,200 square feet and has the option of HEPA and/or charcoal/permanganate air filtration. The Santa Fe Rx is not a rugged unit like the Phoenix 250 MAX. It is quiet and can operate in an occupied space.