Air conditioners need filters to clean debris, such as dust and dirt, from the air. Without a filter, dust and dirt can travel directly to the air conditioner's evaporator coil and cause damage to the system.
Regularly changing the filter on an air conditioner is part of routine maintenance and helps ensure that the air conditioner runs at maximum efficiency. Some types of filters are reusable and can be cleaned, while other types must be replaced completely. An air conditioner that is in constant use or is used in a household with pets that shed may require more frequent filter changes.