All air conditioning systems are equipped with a filter to help trap unwanted dust and dirt and to prevent it from getting into the environment and the air we breathe. Filters should be changed at least twice a year at a minimum, and more frequently if the system is used often or if the occupants of the home are allergy-prone. In these cases, the filters may need to be changed on a monthly basis. If a dirty filter is not replaced, it reduces the ability of the system to function properly and efficiently. Contact your local air conditioning professional for more specific information.