Can You Run A Furnace Without A Filter? (Find Out Now!)

Ossiana Tepfenhart
by Ossiana Tepfenhart

Furnaces are one of the most important parts of any home you go into. Without them, you won’t have heat during the winter and there’s also a good chance your hot water could also be linked to it. (If you have a steam furnace, anyway.) Running them is vital, and so is replacing the filter…or is it? Do you always need to use a filter when running a furnace?

It is possible to run a furnace without a filter, but it should not be done for extended periods of time. Running a furnace without a filter will reduce air quality throughout your home and also lead to permanent damage to your furnace.

Running a furnace without a filter is a major no-no. Filters are there for a reason, and it’s important to understand what that means for your air quality.

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Can You Run A Furnace Without Filters?

You can, but it’s never a good idea. Furnace filters are what keep the air clean in your HVAC system. If you ran out of filters to replace on the furnace, you can usually run it for one to two days with minimal damage. However, long-term use of a furnace without filters is a bad idea.

Is It Better To Run A Furnace Without Filters Or Run It With A Dirty Filter?

In most cases, it’s best to run a furnace with a dirty filter than it is to remove the furnace without a filter at all. Dirty filters can trap air, yes, but they still filter out some of the grit and grime that gunks up your furnace. Assuming that your furnace filters aren’t completely clogged and still have some use, it’s best to keep them in.

How Long Can You Run A Furnace Without Filters Safely?

Honestly, there is no precise amount of time that you are given to before it becomes potentially damaging to your furnace. Most people can get away with running a furnace for one to three days without a filter, but this is something that you should avoid doing if at all possible.

Every time that you run your furnace without a filter, you’re potentially damaging it. At the very least, you may need to give the furnace interior a thorough cleaning afterward. There is no true minimum amount of time you can technically run a furnace without a filter without doing some iota of damage. So, if you do it, do it at your own risk.

Why Shouldn’t You Run Your Furnace Without Filters?

This means that the following things will happen if you remove your filters and start running your furnace:

  • First, you are going to be inhaling dirtier, soot-filled air. Those filters are what trap the soot that comes from burning and heating stuff in your furnace. Even “clean” furnaces will have soot. That soot, unfiltered, will end up in your lungs, your kid’s lungs, and your pet’s lungs. Eek!
  • Second, your furnace will suffer. Soot accumulation is one of the leading causes of furnace failure. Too much soot will cover your furnace’s thermometer, which means that temperature regulation will fly out the window. It also can make it hard for your furnace to keep a flame going, not to mention choke out your motor.
  • Finally, you might not be able to actually keep your temperature regular. Soot makes it very hard for hot air to travel through vents the way it should. This could lead to less hot air going where it needs to go.

How Often Should You Change Your Furnace Filters?

Furnace filters are going to need to be changed at least once per year, if you have five or six inch thick filters. The thinner the filters, the more frequently it will need to be replaced. 1-inch thick filters will need to be replaced every one to three months. Filters that are two to three inches in thickness can be replaced every three to six months.

You can generally look at the size of your filter to determine a good time to replace your filter. In the case of a home where the furnace is older or the airflow isn’t what it should be, err on the side of caution. To make things easier, mark it off in your calendar or have an alarm set for it.

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Related Questions

Should you change your furnace filter more frequently in the winter?

If you use your furnace more during the winter, there will be more soot buildup then. This means that it would make sense to switch out filters more frequently in the wintertine for most of us. Experts agree that you should change a typical household filter at least once during winter—or every three months.

How can you tell if the furnace filter needs to be replaced?

The most common giveaway is  when you pull out the filter and notice that it looks dirty. If it’s all brown and grey, it might be time for a change. Of course, other symptoms tend to show up too. You may notice that your furnace is overheating or that you are not getting the same amount of heat you normally would.Sometimes, a lack of a filter or a need to clean a filter can also result in physical symptoms in people. If you are sensitive to smoke or soot, then the allergies you’re getting could signal that it is time to get a filter replaced.

Is it possible to reuse your furnace filter?

It depends on the type of furnace filters that you have in your furnace. If you have disposable filters (which most homes have), then there is no way to safely reuse your filter. You need to dispose of it. However, if you have a permanent air filter, there is good news ahead.Permanent air filters can be reused—and actually are meant to be washed and reused ad nauseum. This makes them the most eco-friendly option that you can have. We expect to see them more frequently as time passes, though they are still rare now.

Ossiana Tepfenhart
Ossiana Tepfenhart

Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.

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