Indoor mold and mildew is typically caused by humidity, condensation and poor ventilation. Mold spreads through tiny spores that float through the air and reproduce when they land on moist surfaces, so any conditions that increase moisture levels can lead to mold growth.
Indoor mold can be prevented by controlling moisture indoors. Address any plumbing problems as quickly as possible. When water leaks or spills occur, dry wet materials and areas within 24 to 48 hours to prevent mold growth. Keep indoor humidity below 60 percent relative humidity, which can be measured with a humidity meter from the hardware store. Use air conditioners and dehumidifiers if necessary.
Dryers, stoves, kerosene heaters and other combustion appliances all produce water vapor, which increases humidity. To reduce humidity, vent appliances that produce moisture to the outside where possible. Run bathroom fans or open the window when showering or bathing. Open windows or use exhaust fans when cooking, running the dishwasher or washing dishes in the sink.
Reduce condensation by increasing ventilation and air movement. Dry any condensation collecting on windows, walls or pipes immediately, and address the source of the moisture. Open doors and windows when practical, and use fans as needed. Cover cold surfaces, such as exposed water pipes, with insulation. Condensation can also be reduced by increasing the temperature of the air.