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Why Is My Furnace Filter So Dirty?

Determining exactly how often your HVAC air filter needs to be changed isn’t an exact science. Depending on what type of filter you use, months may pass before you need a fresh filter. Every once in a while, you may discover the need for a new filter sooner than expected, leading you to wonder: “Why is my furnace filter so dirty?” Star Heating & Cooling shares some reasons why your filter may fill up sooner than expected and why it’s necessary to change the filter on a regular basis.

Home Come My Furnace Filter Is So Dirty?

Have you recently removed your filter for a regular monthly inspection and noticed it’s much dirtier than normal. Furnace filters don’t always last the same amount of time, even if you’re using the exact same type of filter every time you install a new replacement. Here are a few reasons your HVAC filter can fill with more airborne contaminants faster than expected.

  • Your furnace has been running longer and more often. During the coldest periods of the year, we use our furnaces more than at times when outdoor temperatures are milder. With the heating system cycling more, air is passed through the filter more often, giving the filter more opportunities to trap pollutants. Thus, your filter will fill up faster and must be replaced earlier than at other points during the season.
  • You’re using a low-quality filter. Filters last a varying amount of time depending on their materials and MERV rating. Fiberglass disposable filters rated MERV 1 to 4 typically only last a month or so, while pleated media filters rated MERV 8 or higher can last several months. If you switched to a lower quality filter last time you installed a replacement, don’t expect that filter to last as long as the more efficient filter you previously used.
  • Your system fan is set to “ON.” Typically, you want to keep the system fan set to “AUTO,” which allows the blower fan to run only as the furnace does. If the fan is set to “ON,” it will run all the time, even while the furnace is between heating cycles. This keeps air constantly circulating through the house and heating and cooling system. As more air passes through the filter, the filter fills up faster as it has more opportunities to trap pollutant particles.
  • New pollutant sources were introduced to your home. If your household recently gained a new source of airborne pollution, whether that be a new indoor pet or you’ve made changes such as cleaning less frequently, this can cause the filter to clog faster and become dirtier.

When Should I Change My Furnace Filter?

If you notice a dirty filter, it’s time to replace it. Furnace filters can last anywhere between 30 days and 12 months, depending on their construction and MERV rating. Factors specific to your home also impact how quickly a filter will fill with contaminants, such as how often the HVAC system is used and sources of air pollution present inside.

To ensure your filter is replaced as often as needed, don’t just rely on the filter manufacturer’s recommendation to tell you how frequently your filter should be changed. Instead, inspect the filter monthly by removing it and checking it over visually. If there is clean space left on the filter’s surface, it can still be used. If the filter is completely dirty, go ahead and dispose of the filter and install a new one.

Why Is It Important to Change Your Furnace Filter Regularly?

For your furnace to work efficiently, air needs to move properly through the HVAC system. Regular filter replacement is an important part of good furnace maintenance. When air filters become clogged with pollutants, they restrict airflow through the heating unit and home. A dirty filter that blocks airflow causes all sorts of problems for your furnace, including:

  • Forcing the system to work harder to circulate air through the system, which wastes energy.
  • Without proper air movement, temperatures may climb too high inside the furnace, causing the furnace to overheat and shut down – this can cause damage to furnace components.
  • When the filter blocks air movement, you may not receive enough heat indoors to keep rooms at a comfortable temperature.
  • When the filter is completely clogged, it does not have space to capture new pollutants passing through the system – these particles can settle inside the furnace where they may damage components or circulate back into your living areas, diminishing your home’s indoor air quality.

Contact Star Heating & Cooling for Furnace Services

Star Heating & Cooling wants to help you maintain your furnace, through regular filter changes and professional maintenance services. Annual tune ups are an important part of keeping your furnace running properly – contact us today to schedule service services for your heating or air conditioning system.