A dirty air filter can cause a range of problems for your home, from allergens building up in the duct system to mold growth and even a fire hazard. Not only will the air not filter properly, but it can also lead to ice formation on the coils, reduced energy efficiency, and decreased indoor air quality. The amount of strain caused by a dirty filter means that the motors in your systems are working longer than they were designed to work. A clogged air filter restricts airflow in the air conditioning system, preventing air from entering and leaving the system, reducing the internal temperature of the unit.
This will affect the ability of the air conditioning system to generate heat and will result in ice formation on the evaporator coils. Reusable filters can be washed and replaced. However, disposable filters aren't meant to remove water after they get wet. The moisture that the filter retains can encourage mold growth over time, and the HVAC system could spread mold spores throughout the rest of the house.
Plus, wetting a disposable filter makes it much less effective, so you'll see decreases in energy efficiency and indoor air quality. Central air conditioning relies on continuous air recirculation. When that airflow is hampered by a dirty or clogged air filter, it means that your system has to work a lot harder to cool your home. The harder the system has to work to extract air throughout your home, the more energy you need and the higher your energy bills. The only type of filters that trap allergens and spores are HEPA, or high-energy particulate air filters.
Particulate capture efficiency increases as the filter becomes dirty; buildup in the fibers reduces the openings through which air passes and allows the filter to capture more particles. One of the purposes of an air filter is to filter out all microscopic particles such as dust, pollen, pet dander, bacteria, plant spores and mold, and even smoke. If the air filter is dirty and you have problems with the air conditioner, most of the time it always returns to the clogged filter. If you haven't cleaned or changed your filter in a long time and your air conditioner hasn't blown cold air like before, it could mean that the system has frozen. If you leave the filter on for too long, it may become so clogged that it is absorbed by the HVAC system. Not only will this prevent proper filtration of air but it can also pose a fire hazard to your ventilation. In a nutshell, every time your system is forced to work harder due to a clogged or dirty filter, it's costing you dearly (PLUS, you get less air for the money).
To avoid these issues and keep your home safe and comfortable, make sure you clean or replace your air filters regularly.