How Often To Change Furnace Filter


One of the best furnace maintenance tips is to change its filter regularly. Most people change their furnace filter every six months, while others may change it in three months. There are no one-size-fits-all solutions to furnace maintenance. How often you need to change your furnace filter will depend on factors like your location and the device model.

You’ll need to change your furnace monthly if you live in a dusty environment. But in areas with less dust and homes with no furry pets, you can wait for up to three months before changing the furnace filter.

All the questions you have about when to change the filter are important, not just for the furnace’s performance. A dirty furnace filter can also adversely effect household occupants.

A dirty or clogged filter can also cost you bigger furnace repair expenses if you don’t change it promptly. This article contains other important information you need to know about furnace filter maintenance and its role in keeping a functioning furnace.

When to Change Furnace Filter

A furnace filter or air filter keeps your furnace in good working condition due to the critical role it plays. Furnace filters protect your furnace, especially the blower fan, from debris, hair, and other pollutants the return duct takes in.

Changing your furnace filter undoubtedly improves your home’s indoor air quality (IAQ). The problem is no manual states exactly when to change the filter. Furthermore, there’s no specific time of the year to change your filter. The only hard rule is to change your furnace filter at least once every three months.

Your furnace work rate can also determine the best time to change its filter. For instance, every home runs its furnace for a different number of hours. The more the furnace works, the faster you have to change the filter. Therefore, some households may need to clean or change their furnace filter more often than others.

Also, every home has a different amount of dirt, allergens, pet dander, and dust in the air. The presence of children or pets in your home increases the chance of more air pollutants clogging your furnace filter. These seemingly insignificant factors contribute to your furnace’s performance and how long the air filter will last.

How to Change the Furnace Filter

Replacing the furnace filter is one task you can do by yourself. You simply need to follow the steps below.

Put Off the System

Turning off your furnace is the first line of action whenever it’s time to replace the air filter. It makes the furnace safer to carry out the filter changing process. Furthermore, it’s important to always turn off appliances before any repair or replacement to avoid electrocution or other system malfunction.

Even expert furnace repair technicians turn off the system before working on it. They know how dangerous electricity can be and have a healthy respect for it. That’s the mindset you should have before trying to change the filter.

Remove Filter From the Return Air Vent

The next is to take the filter out of its position (return air vent). Normally, the filter should have indicators showing how to insert it into the furnace. But, you want to pay special attention to the filter’s position while removing it. You’ll find it easier to place the replacement filter by doing so.

Replacing or Cleaning The Filter

A disposable filter demands ingdiscarding the old clogged one and fitting the new one by observing the arrows or indicators.

If your furnace filter is the permanent type, you need to clean it. To do that, start by taking the filter outside. You’ll need to use a nylon brush if it’s too dirty and has a layer of debris on it. But be careful not to go too hard on the filter. You just have to tap the dirty filter on the surface to dislodge more debris and dust.

It’s important to be gentle because cheap filters aren’t that strong. Most of them are just flimsy cardboard frames with little thin wires to hold the fibreglass in place. It’s easy for these filters to suffer damage. And when the frame bends, it becomes difficult to get the filter back into its position.

But, if the filter has a high Minimum Efficiency Reporting Value (MERV), you can apply moderate pressure when cleaning. Check whether the force you’re applying is destroying the pleats on the filter. You can continue with the cleaning step if the pleats are fine. Finally, vacuum the filter with a stiff brush accessory.

Use Compressed Air

An air compressor makes the entire furnace filter cleaning process easier. Compressed air is a superb tool for cleaning any type of filter. But experts claim that compressed air works better with a MERV filter. You can use compressed air from the opposite direction as the airflow indication on the furnace filter.

The next step is to focus the compressed air onto the filter away from you (on the neat side of the filter). To do this, you need to hold the arrow pointing toward you. You’ll notice the air blowing off dust and lint from the dirty side of the filter. Once the filter is clean enough, you can place it back on the furnace.

Related Article: How to Clean a Furnace

Should I Change My Furnace Filter?

Change My Furnace Filter

An unclogged filter is important to keeping your furnace in optimal working condition at all times. There’s no hard and fast rule to changing your furnace filter, but there are general recommendations that can help you maintain a good furnace filter-changing habit.

Here’s how you can know whether or not you need to change your furnace filter:

Check the Filter Every 30 Days

A good routine you can maintain is checking your furnace filter every 30 days (monthly). Maintaining such a habit helps you avoid filter-related issues with your furnace, especially if it works constantly.

Every month, checking your furnace filter will help you determine if it’s still filtering dust and particles from the air. It’ll also help avoid breakdowns that can cost a lot of money to fix.

You can also spot a bad filter by its colour. For instance, once the furnace filter turns greyish, you know that it’s due for a change. It’ll also have a build-up and appear dusty from all the particles it’s been accumulating.

Change Your Furnace Filter in 90 Days

Ultimately, you need to change your furnace filter every three months (90) days. You must practice this maintenance task to ensure your filter and furnace performs optimally. Checking the filter monthly is ideal, but it’s inadvisable to continue using the same filter for over three months without changing it.

Exceeding the three-month interval equals risking a breakdown of the entire furnace system. Your health will also be at risk. Everyone in the home will keep inhaling unhealthy air, leading to health problems. Therefore, changing your furnace filter every three months will save you a lot of stress and money in the long run.


It’s important to pay extra attention to your furnace filter if you own pets. The more furry animals you have in your home, the shorter your furnace filter’s lifespan.

It’s well and good to snuggle furry animals. However, all the extra hair has to go somewhere. If the vacuum doesn’t catch it, your furnace will have to filter it. Pet hair is one particle that clogs a furnace filter fast.

There it’s important to maintain a monthly check to clean or replace the furnace filter. Keenly adhering to this routine will help your system function effectively and efficiently, thus maintaining or increasing its lifespan.

A one or two-inch furnace filter requires changing every two months. Then, four months for a four-inch filter, and for a five-inch filter, it’s six months. Having many pets affects how often you’re to change your furnace filter.

Every month, homeowners with multiple pets need to change their one or two-inch furnace filter. Instead of six months, change your furnace filter every three months if it’s a five-inch model.


There is no loss whenever you invest in good health, and one of the ways you can do that is to change or replace your furnace filter regularly. You should consider buying a higher-quality furnace filter if a household occupant has allergy problems. Installing a better standard of furnace filter costs higher. But, it’s an effective method of reducing allergens.

Regularly Open Windows and Doors

Homes with doors and windows that are regularly open are more prone to furnace filter clogging issues. Open doors allow the free flow of dust and other particles into your home, making your furnace filter clog more often.

Homeowners in this situation need to replace one and two-inch filters monthly and four-inch filters every two months. For the five-inch filters, you need to replace them every three months.


A home with a smoker is likely to have filter problems more frequently. The more smokers around, the more issues you’ll have with your furnace filters. The lifespan of the furnace filter will be shorter than usual due to the smokers in the house.

Smokers may have to change a one or two-inch furnace filter once every two months. For a four-inch filter, you need to change it every four months. Finally, twice a year will do for the five-inch filter.


Dust is an important factor that can reduce the lifespan of your furnace filter. You have to change one and two-inch furnace filters monthly if your house is always dusty. The best time to change four and five-inch furnace filters in dusty environments is once every three months.


Effects of a Dirty Furnace Filter

Before air enters the system, it passes through the filter. The furnace filter will then remove dust, contaminants, and other particles that can cause bigger problems if they get into the system. As a result, the filter will become dirty.

See the effects of a dirty filter below.

Hike in Energy Bill

Your furnace works thanks to constant air recirculation. You need to change your furnace filter because it can restrict the airflow in your furnace. The system has to struggle harder to perform its job due to airflow restrictions.

The more the system struggles to work, the more energy it zaps, resulting in higher energy bills. Simply put, a clogged filter will cost you more to run your furnace.

Poor Air Quality

A furnace filter either augments or negatively affects the air quality in your home. A furnace filter sieves microscopic particles like dust, bacteria, pollen, and pet dander. When your furnace filter is clogged, it will recirculate these particles into your home, causing you and your family health issues.

Everyone in your home may experience cold-like symptoms, fatigue and headaches. Having such health issues in your home indicates that the furnace filter is due for a change.

Air Flow Restriction and Strain on Blower Fan

Blower fans push air through the furnace filter. A clogged filter will cause the blower fan to work harder than normal to pass air. It also requires more energy which will reflect on your utility bill significantly.

A clogged filter and strain on your blower fan can cause it to burn out. You may also start to experience unsteady room temperatures throughout your home.

System Failure

A blocked filter not only has the capacity to damage one or two components but can also bring down the entire system once the air blower gives way. You may end up spending thousands of dollars on repairs due to a clogged filter.

How Much To Replace Furnace Filter

On average, it costs $50 to $150 to replace your air filter, depending on the furnace type. Regularly changing your filter saves you lots of repair expenses which range from $150 to about $2,050 (evaporator coil).

Your system will also have an increased lifespan. It’s wiser to maintain a proper routine check for the wellness of your furnace. Doing so will help you save money on higher repair costs in the future.

Related Article: Buying a High-Efficiency Furnace

Final Thoughts

The role an air filter plays is critical to your furnace’s overall well-being and performance. It shows the importance of maintaining a regular furnace check monthly, every two months, and three months or even six months.

Changing your furnace filter is one of the DIY tasks you can practice on your furnace considering how easy it is to replace. As explained, when to check or replace your furnace depends on its model and your location. However, you can always use our expert furnace repair technicians if you have any issues.

Here at ALP Heating, we can handle your furnace’s periodic maintenance needs. Call us today to replace your furnace filter and keep the appliance in great condition.

ALP Heating is committed to providing the finest service possible to important areas. We are delighted to be your go-to cooling and heating business for all of your requirements. Because of our commitment to perfection.