Can Your Furnace Run Without a Filter?


By John C. Flood


A furnace filter doesn’t just purify your air, it keeps the inner mechanisms of your HVAC system functioning properly. Without a furnace filter, dirt, dander, and debris won’t be cleaned out of the air, which can be bad for you and your family’s health. Also, if you fail to replace a clogged filter, it can wear down your heating system. Luckily, these filters are easy to change, making this a quick, painless home maintenance task that drastically improves furnace airflow.

What is the importance of a furnace filter?
Air that is heated and circulated through your home has to pass through a furnace air filter, which consists of tightly woven fiberglass, paper, or cloth elements. This creates a semi-permeable blockade that traps harmful particles.

A clogged air filter prevents air from flowing through the system which can lead to:

• Cold indoor temperatures even with the heat turned on.
• Poor airflow.
• Expensive utility bills.
• Worn-down HVAC system.
• Overheated furnace.

What is the risk of running your furnace without a filter?
If you run a furnace without a filter for one night, it won’t affect your HVAC system detrimentally. However, the longer you run your heating system without an air filter, the more contaminants will accumulate inside your heating unit’s inner mechanisms.

Poor air quality.
The most prevalent issue that stems from running a furnace without a filter is poor indoor air quality. Dust is stirred in a home when the furnace continually cycles the air. Debris is sucked back up through the intake, pumped back through the air vents, and remains suspended in the air until it is inhaled or accumulates within the HVAC unit.

Contaminated ductwork.
Without a filter, pollutants and air toxins will travel throughout the ductwork. The debris will accumulate inside the ductwork, becoming trapped by the ribbed aluminum tubes. This accumulation will harbor moisture within the ductwork, creating the ideal conditions for mold to grow. Mold spores will begin to circulate throughout your home whenever the HVAC system is running and be extremely dangerous to occupants within the household.

How often should you replace a furnace air filter?
How often you replace your furnace filter depends on the size of your home. Check your HVAC filter once a month to ensure it’s not clogged, especially during the heavy-use winter months. Whenever the filter appears dirty, it’s important to replace it.

At a minimum, change the filter every three months to improve heating efficiency. Here are some tips on how to change your furnace filter:

Locate your filter.
Shut off your furnace to be safe before opening up your furnace. The furnace filter is either inside the furnace itself or inside the return air vent. Remove the service panel to view the filter. Check the furnace manual if you cannot locate the filter.

Identify the replacement filter type.
The frame of the old filter should display the size, which can vary depending on the unit size and model. Reference your furnace manual to determine what type, size, and thickness of the filter you need for your home’s furnace.

Remove the old filter.
If you have a new filter, throw away your disposable filter and replace it. If your filter is reusable, wash it off and replace it. Your old filter should have arrows noting what direction the air flows to help you insert the new filter the same way.

Secure the new filter in place.
Remove packaging from the new filter so the air can flow through. Slide the filter into place, ensuring the arrows on the frame point the same direction as the previous filter. Close the service panel and turn the furnace on.

If you choose to run a furnace without a filter, you leave your heating system susceptible to dirt and debris that will inevitably lead to expensive repairs and premature death of your HVAC system. Trust your home to the John C. Flood team to ensure your home’s air quality is top-notch. Their HVAC professionals will take care of all your furnace filter maintenance. Schedule your inspection today!


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