Duct cleaning generally refers to the cleaning of various heating and cooling system components of forced air systems. This includes the supply and return air ducts and registers, grilles and diffusers, heat exchangers heating and cooling coils, condensate drain pans (drip pans), fan motor and fan housing, and the air handling unit housing. This is done to ensure that the levels of indoor air pollution is low and the air quality is of acceptable standards. Charges for this service depends on the size of the system to be cleaned, system accessibility, climatic region, and level of contamination. Sometimes, the provider may also use a biocide or certain chemicals to help ease the dirt off the ducts. One should get air conditioning ducts checked on a regular basis, especially if someone in the household suffers from allergies or unexplained symptoms or illnesses. A visual inspection of the ducts can also help. Ducts should also be checked and cleaned if there is visible mold growth, infestation with vermin, e.g. (rodents or insects) or they are clogged with excessive amounts of dust and debris and/or particles are actually released into the home from your supply registers. Timely cleaning can help maintain the functionality of the air conditioning unit at its optimum levels.