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Why Replacing Air Filters Is So Important

Looking at an air filter for a furnace or air conditioner, it doesn't seem like it's something to be too concerned about. Usually square or rectangular and an inch or so thick with a cardboard frame containing a fiberglass material or some sort of pleated cloth, there's nothing interesting or exciting about an HVAC system air filter. Despite their modest appearance, however, air filters are actually extremely important components of forced-air home heating and cooling systems. Here's a brief overview of the function and features of air filters and why replacing or cleaning them regularly is so important to HVAC system operation.

The Basics of HVAC Air Filters

Air filters in your heating and cooling systems help clean the air in your indoor environment. They capture and hold airborne particulates such as dust, hair, fibers, mold, pollen and other material that could cause respiratory irritation and degrade indoor air quality. Without an air filter, these materials can freely circulate inside your home and coat HVAC equipment and components.

In essence, the HVAC system is a very large air circulation system. Conditioned air is generated by the equipment and sent into your home through supply ducts by a powerful fan or air handler. Expended air returns to the system through return ducts and is conditioned and distributed again. It's during the return air process that the air is forced through the air filter, where it's cleaned before being reconditioned.

Air filters usually contain a type of spun fiberglass or pleated cloth. Fiberglass is very common and usually provides adequate filtration for an economical price. Cloth filters can cost more, but they provide better air filtration in general.

Besides filtration, air filters help maintain proper airflow within your heating and cooling system. This airflow is necessary for correct and efficient operation of the equipment. Interference with or blockage of the airflow can cause serious problems, from system malfunctions to complete breakdowns.

Maintaining Air Filters

One of the easiest and most important elements of HVAC preventive maintenance is changing the air filters regularly.

In general, air filters should be checked every month, particularly during time spans when the furnace or air conditioner is in operation. If the air filter is dirty, it should be changed. If it's still clean enough to function, the air filter can be left in for another month or two, but it should be changed as a matter of course every three months. If your indoor air is particularly prone to airborne contaminants, it may be necessary to change the air filter as often as twice a month.

As the air circulates through your HVAC system and flows through the air filter, particulates in the air are caught and held within the cloth or fiberglass filter medium. Over time, these particulates build up on the filter. When they do, less air can make it through the filter medium and fewer particulates can be captured. Finally, the air filter gets so clogged that very little air can make it through. When this happens, the furnace or air conditioner can be damaged by the lack of airflow, plus dirt and debris may blow past the filter into your airstream. A dirty air filter can cause the HVAC system to malfunction or break down, requiring costly repairs that could have been avoided.

Dirty air filters can also reduce system efficiency significantly, increasing the amount of energy and money it takes to produce heating or cooling. They can impair the performance of the equipment, reducing your indoor comfort level. They can let more and more airborne contaminants into your indoor air, affecting respiratory health.

Air Filter Efficiency

Not all air filters are created equal. Air filters have efficiency ratings that indicate how effective any individual filter will be at capturing and holding airborne particulates. Common air filters are rated by minimum efficiency reporting value, or MERV. MERV ratings range from 1 to 16, with higher numbers indicating a greater ability to capture smaller and more particulates. Most household filters have MERV ratings between 1 and 8, though those rated MERV 1 to 4 are generally useless when it comes to improving indoor air quality. Many experts suggest a filter in the MERV 8 to 12 range for a good combination of air-cleaning ability and airflow maintenance.

There are also even higher-efficiency filtration systems, such as high efficiency particulate air (HEPA) filters, that provide filtration at MERV levels from 17 to 20. These systems are very effective, but they typically require specialized installation and system modification. They're not commonly used in residential settings, though they do work well in standalone air cleaners and vacuum cleaners.

Higher-efficiency filters are more effective at cleaning indoor air. Keep in mind, however, that better air filters can also impede the airflow in HVAC equipment. Before installing a high-MERV filter, make sure your furnace or air conditioner can handle a denser and more effective air filter. Otherwise, the reduced airflow could damage the equipment.

For help finding a West Texas HVAC contractor near you, contact us today.

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