Air conditioners can help reduce the entry of allergy-causing pollen. But they may also become a source of biological pollutants if not properly maintained. Clean the coils and incline the drain pans according to manufacturer's instructions, so water cannot collect in pools. Have furnace-attached humidifiers cleaned and serviced regularly by a professional, especially before the heating season. Follow manufacturer's instructions when using any type of humidifier.
Experts differ on the benefits of using humidifiers.
For larger portable humidifiers, change the water as recommended by the manufacturer. Unplug the appliance before cleaning. Some manufacturers recommend using diluted household bleach for cleaning and maintenance, generally in a solution of one-half cup bleach to a gallon of water. When using any household chemical, rinse well to remove all traces of chemical before refilling humidifier. Empty dehumidifiers daily and clean often.