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How Long Does a Furnace Filter Last?

A furnace filter is one of the most important parts of your furnace. Most furnaces come equipped with a standard one-inch filter, this filter can be found in the blower compartment of the furnace. Typically, this is located in the bottom or side of the unit. The filter needs to be changed periodically so that your heating and cooling system can work its best and so that the air inside of your home stays clean and well circulated.

A filter is the median that cleans the air before it touches the electrical components inside of your system such as your fan blower. When the furnace filter becomes clogged with contaminants, air cannot circulate properly through the system. This causes the fan blower and other components to work harder as they draw more energy to do their work. Drawing of more energy can lead to higher bills as well. The components are also more likely to wear out from the strain. A dirty filter is usually one of the top reasons for unnecessary service calls and can cause your system to run the risk of overheating and freezing. In addition, you should never run a furnace without a filter because dirt and other debris can easily bypass through and can lead to serious damage to your HVAC system and cause it to fail prematurely.

A filter is not only an essential part of your HVAC system but extremely helpful for pet owners, anyone with allergies, and for people that enjoy using candles. It is important to change out these filters on a regular basis for best results.


A good filter can remove dirt, dust, and other allergens from the home quickly. It can offer relief for many people who have allergies or for those who have mold spores in their home. This relief happens when the filter traps the allergens & airborne particles. By trapping these triggers, it eliminates them from the air, thus reducing symptoms caused by allergies.   If you have allergies, a good filter with higher MERV ratings can make a huge difference. MERV stands for Minimum Efficiency Reporting Values, these values report a filter’s ability to capture larger particles between 0.3-10 microns. The value helps consumers compare the performance of different filters. Essentially, the better a filter is at trapping certain types of particles the higher its MERV rating will be.
(chart courtesy of EPA.gov)

Pet Owners

Pet owners can appreciate filters since it will help keep their air healthy for their family and pets. Pet dander and fur can be filtered out through the HVAC system so that your home is a healthier place to breathe. When considering a filter change, you may want to look at how much your pet sheds or how many pets you have as that can be a factor on how many times you will need to check or replace your filter. Pets might also be an excellent reason for considering an upgraded or higher MERV filter for your HVAC system.


Although candles can smell good and help improve the ambience in any room, they can also lead to an unhealthy quality of air. Smoke and soot can end up clogging your air filters. If you want to burn candles and have clean air, changing out your filter on a routine basis is going to be a smart choice.

Change Your Filters Regularly

Each filter will have a different lifespan. You can buy filters that can be washed and reused, or you can change out filters with fresh ones as recommended by your manufacturers owner’s manual.  When it comes time to replace a filter you should know roughly how long each filters lifespan is and take into consideration our home’s environment, family’s allergies, pets and candle use among other factors.

For example, a one inch furnace filter should be changed out every one to three months. A three to four-inch filter can last for six to nine months. If you have a thick five to six-inch filter, it can last from nine to twelve months. By making sure that your filters are changed when they need to be, you can enjoy having a heating and cooling system that will work its best. You can also appreciate having clean air that will be easy to breathe in.

We recommend checking your filter monthly to see if it needs to be changed out. If your filter needs to be replaced, you will notice its off white color and it will most likely have visible dust and particles collected in it (as shown in the picture).

(Clean Filter vs Dirty Filter)

What Size Filter Is Best For You?

It is always good practice to start with your manufacturer. Keep in mind, using a filter that is too thick for your system is also not good as it impedes and restricts air flow. Depending on the furnace brand or model series they may recommend different filter sizes for your unit. If you still are unsure or feel you would benefit from a better-quality filter, you should contact one of our HVAC professionals. They will be able to provide you with a recommendation of what filter would be best for your system and household needs. If higher efficiency if your goal, they can also install a cabinet that will be attached to your furnace which would allow room for the upgraded (higher) MERV filters. The filter cabinets are used to fit thicker filters, while providing easy access to check or replace them as needed.

Call Us Today

If you are interested in learning more about filters for your furnace, we can help. Contact Christian Heating and Air Conditioning today at (215) 488-5795 to have all of your questions answered or to set up an appointment with one of our professional HVAC technicians.



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