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By Joanna Brown
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Posted 8/1/23

The air filter, also called a furnace filter, is an integral component of your HVAC system. It’s not permanent, and must be replaced on a regular basis to do its job. Our HVAC FAQs address the important points you need to know to better understand how the air filter works and how to take care of it properly.

Replacing Furnace Filter

HVAC FAQ: What Are the Different Types of Furnace Filters?

Furnace filters come in many shapes and sizes so you can find the best solution for your air quality needs that fits your HVAC system. Filters protect delicate system components from airborne contaminants that could cause mechanical failures. By removing these contaminants from your indoor air supply, they also work to improve air quality.

The different types of furnace filters include:

Fiberglass/Synthetic Filters

Fiberglass or synthetic filters are a cheap and disposable option for your furnace. They catch up to 80% of particles 50 microns and larger and 25% of particles between 3 to 10 microns. Considered minimum protection, fiberglass/synthetic filters prevent dust and dirt from building up on heat exchangers, fan motors, and other surfaces. The larger particles are trapped and eliminated, so your furnace components remain clean. They allow your system to have maximum airflow but don’t filter harmful contaminants affecting your health.

Polyester Filters

Polyester filters are made using the highest quality materials available and are median-sized. They trap and eliminate 80% to 95% of particles 5 microns or larger. A polyester filter costs fours time more than the average fiberglass/synthetic filter, but it offers more protection against pollutants that cause health issues.

Electrostatic Filters

Electrostatic filters use self-charging fibers to attract particles out of your air. You can purchase disposable or washable electrostatic filters depending on the requirements of your furnace. Washable versions offer a MERV rating between 4 and 10 and last considerably longer than the average filter. Maintenance on a washable filter requires soap and water to wash the filter and letting it completely dry before reinstalling it. If you install it before it completely dries, you run the risk of mildew and mold growth.

Pleated Filters

A pleated filter offers high-efficiency results by trapping particulates 0.3 micron in size, such as bacteria and viruses. Pleated filters are more efficient and last longer compared to fiberglass/synthetic filters. They eliminate more pollutants from your air without sacrificing airflow within your system.

HEPA Filters

High efficiency particulate air, or HEPA, filters provide high-end filtration by trapping up to 99% of particles 0.3 microns or larger. Even though they are excellent at eliminating indoor pollutants and create a healthier environment in your home, they can drastically reduce your system’s airflow, costing more money in energy usage.

HVAC FAQ: Why Is It Important to Have Good Quality Air Filters?

With a good quality air filter in your system, contaminants in the HVAC equipment as well as in the home will be kept to a minimum. A good quality filter also helps your heating and cooling equipment perform more efficiently.

A good quality air filter comes with the following advantages:

HVAC FAQ: How Often Does My Air Filter Need Changed?

The frequency your air filter needs changed depends on the type of filter you use and factors relating to your household environment.

Most filters have a recommended guideline detailing how long they last or when they should be changed. When you purchase a new filter, check the packaging for these details. The standard time recommended to change a high-quality air filter is at least once every three months. However, if the filter appears dirty, change it immediately! Dirty or clogged air filters prevent healthy air flow, damage components inside your air conditioner, and decrease your system’s efficiency.

Remember to Change Your Furnace Filter

If your filter doesn’t indicate when it should be changed, there are some factors to consider when deciding how often to change it:

When you have more contaminants in the home, from pets, people, and activities, air filters should be changed more frequently.

HVAC FAQ: How Can I Tell if My Air Filter Needs Changing?

Air filters need to be changed on a regular basis to be effective. The manufacturer will recommend the frequency the filter should be replaced, but other factors may warrant a change sooner. Watch for these signs that your furnace filter needs changing:

Replace Dirty Furnace Filter

HVAC FAQ: Can I Run My HVAC System Without an Air Filter?

While your heating and cooling system will run without a filter, you definitely shouldn’t do it. Running your HVAC system without an air filter can cause serious problems, such as:

Condensate Drain Problems:

Without a filter for your air conditioner, your condensate drain won’t be able to perform its job of draining condensation and moisture from your unit. Condensate accumulates on the Freon tubing and then drips down to the pan. The pan drains outside and helps your air conditioner with dehumidifying the air in your home. The filter keeps debris from gathering in your condensate drain and clogging it, causing water damage to your system.

Air Quality Problems:

The most common problem with running an air conditioner without a filter is decreased indoor air quality. Dust is stirred in a home when the AC unit is running and continuously cycles throughout the air, never settling. The dirt, dust, and debris is sucked back up through the intake, pumped back through the air vents, and remains suspended in the air until someone breathes it in or it clogs the unit.

Freon Tube Problems:

An air conditioner pulls air from your home and blows it across copper tubes filled with Freon. These tubes are always wet and when unfiltered air blows across them, dirt and debris stick to the condensate and coat the fins. When this occurs, your system performs inefficiently and overloads your air conditioning system.

Ductwork Problems:

Any dirt and debris that doesn’t stick to the Freon tubes will travel down the line to your ductwork. The debris will accumulate inside the ductwork, becoming trapped by the ribbed aluminum tubes. This allows moisture to build up inside your ductwork, creating the perfect place for mold to grow. Mold spores will begin to circulate throughout your home whenever the HVAC system is running.

Get Answers to HVAC FAQs on has the answers to all HVAC FAQs on our website! If you have a question that’s more specific to your home, working with a trusted local heating and cooling contractor will give you the clear answers you need to care for your home and system.


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