Why Is My HVAC Air Filter Always Dirty?

Homeowner’s know that one of the major responsibilities of maintaining the wellbeing of their air conditioning unit is to replace the air filter in a timely manner. The recommended time to change your filter is every 1 to 3 months. Many HVAC systems are connected to smart thermostats that may allow you to set a reminder of when to replace your filter, or sense when the filter needs replacing based on air flow.

If you have ever noticed that your filter is extremely dirty every time you change it out, try replacing the filter more often. For example, if you were replacing it every 3 months, try every 2 months, or if you were doing it every other month, then replace the filter once a month.

However, in some homes, the filter may continue to be clogged up before its schedule time for replacement. So, why does your HVAC filter get dirty so quickly? The purpose of an air filter is to remove the dirt, dust, dander, pet hair, and other debris from your air as it is collected through your home and passed through the system for cooling. There are a number of causes that can make the air in your home dirtier than average, causing your filter to get clogged ahead of schedule.


If you have one (or more) furry pet who has a shedding problem, they are a major contributor to your air quality. Sweep hardwood or tile floors daily or every other day; for carpets, try to vacuum at least once a week. Also, using a de-shedding brush on your pet once a week will also reduce the hair they put out into your home. If your pet is frequently outdoors, try to brush them before you let them to reduce the amount of dirt and pollen they track into your house.


It collects everywhere and always seems to be in your home no matter what you do. Even when you try to wipe down surfaces, some of it still manages to escape back into the air. Some rooms just collect more dust than others and anything not sucked up in the vacuum or removed on the rag during cleaning can end up in the filter.


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High MERV rating

The higher the MERV rating, the better the filter is at catching smaller particles floating in your air. This also means it can become more clogged than a lower rated filter in the same amount of time. This doesn’t mean you should go with a lower rating however, but you can try to find ways to reduce the particles in the air to extend the life of your filters (such as reducing the dust or pet hair in your home). Or, you can adjust to frequent filter changings and enjoy your clean air.

Your air is “on”

When the thermostat is set to “on” rather than “auto” that means that your fan is constantly pulling air through your home, through the filter, and pushing it back out again, even if it isn’t cooling it because the air is already at the right temperature. The more air that passes through the filter, the more likely the filter is to get clogged sooner. You can change the setting to “auto” and the air will only pass through your system when it needs to be cooled.

It’s hot out

Warmer temperatures outside mean that your system is going to have to work more often to ensure that the air inside of your home is kept at the specified temperature. Which means, air is constantly having to pass through the filter, clogging it up sooner. If you don’t want your AC working overtime, up the thermostat a degree or two.

Also, if you find that your filter is still clogging up ahead of schedule and you’ve tried all you can or are willing to do (not everyone wants to switch to “auto” or sacrifice a few degrees for the sake of their filter) then you may want to consider switching to reusable filters. They are initially more expensive, but over the long run, you’ll be saving yourself some money if you have to change your disposable filter 1 to 2 times a month.

Finally, if  you want more orientation or you want to request a service, please do not hesitate to contact us to receive more information about it!


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Last modified on December 14th, 2022 at 10:44 am

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