What Can Happen If You Don’t Change Your Furnace Filter Regularly?

Most Americans rely on some form of furnace to heat their homes. Despite how common these devices are, many people are unfamiliar with their regular maintenance needs. For example, are you aware that your furnace has an air filter that requires regular replacement?  For those who didn’t know, you likely thought to yourself, “Oh no. What if I haven’t?”  Well, that’s what we’re going to answer today. We’re going to take a look at what happens when a filter is not changed regularly, and what that can mean for your furnace and your home. 

Decreased Efficiency

Your furnace’s air filter blocks dust and dirt from entering the return duct of your furnace. This is the duct that sucks air from your home and returns it to your furnace. You can think of it as how your furnace inhales.  So, your filter keeps debris from entering your furnace or clogging important ductwork. However, when a filter goes on unchanged, caught dirt and debris build up and make it difficult for your furnace to take in air. Your furnace then has to work harder and longer to heat your home due to reduced air intake.  This all means, with a dirty furnace filter, you’ll have to pay higher energy costs to achieve the same quality of heating from your furnace.


On a more serious note, a dirty furnace filter also causes many safety concerns for your home.  The most concerning of these is the risk of fire. The debris caught by your filter can be highly flammable, and you must remember that this filter blocks a duct that leads to a high-heat environment. Should a large clog of debris from an unchanged filter catch fire, it would pose a serious threat to your home. 

Reduced Air Quality

Again, your furnace filter catches the air debris from your home before it’s cycled through your furnace. This includes allergens, dust, pet hair, and the like. The filter is designed to prevent these from re-entering your home’s air.  However, a dirty, unchanged filter will eventually do the opposite as air is pushed through it and back into your home.  Think of it as running water through a dirty towel. Rather than the towel catching detritus as water runs through it, the water picks up dirt from the towel as it flows through. That’s what happens to your air quality when you leave a dirty filter for too long. 

Unit Damage

A dirty filter will also eventually lead to damage to your furnace from short cycling.  Short cycling occurs when a dirty filter or any other obstruction causes decreased airflow to trap heat in your system. The resulting temperature will continue to rise until it activates the limit switch to prevent overheating. Although this mitigates the problem, the root will problem (a dirty filter) will continue to exacerbate the situation. Until this is fixed, your furnace will continually overheat again and again.  Frequent and continuous short cycling will cause several problems with your furnace. This includes the inefficiency we discussed early as short cycling will cause your furnace output to drop.  However, over time, this will become more serious. Short cycling causes wear and tear on your furnace which will eventually cause breakdowns. Even after repairing these breakdowns, the problem will continue without replacing your filter. This severely reduces the lifespan of your furnace.  The sooner this problem is corrected, the longer you’ll have before you’ll need to replace the furnace. 

How Often Should I Change My Furnace Filter?

To avoid these problems and a lot of headaches, simply incorporate furnace air filter replacement into your regular home maintenance routine to prevent clogs to begin with.
However, the frequency of which you need to replace the filter will vary by home and region.  To safely find the interval your filter needs replaced, begin with monthly checks following a replacement. Count these months until you find a replacement is necessary. This will be the interval at which you can safely wait to replace your furnace filter. 

The Bottomline 

Filter replacement is a necessary part of regular furnace maintenance. This will save you frustration and money over the lifetime of your home’s furnace. If you’re unsure of your last filter replacement, it’s time to check. If you schedule a fall furnace maintenance, we will check the status of your filter and show you how to replace it. Our highly trained HVAC technicians can also make recommendations as to which filter will work best based on your needs. And, as always, if you are experiencing issues with your furnace, give us a call. We are here to help!