How to Change an Air Filter

HVAC Logo IconBy Tom MoorJune 8, 2024
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HVAC technician holding air filter

Locating and Replacing Your HVAC System’s Filter Takes Less than 10 Minutes

You may be aware of the importance of regularly replacing your HVAC system's air filter. If you’re a new homeowner or not familiar with home comfort systems, though, it’s easy to overlook this task.

Big deal, right? In actuality, changing your air filter is a huge deal. A clogged and dirty filter restricts airflow that can cause your HVAC system to strain, leading to inefficient airflow and potential malfunctions.

The good news – changing your furnace filter is a simple DIY task that only takes a few minutes. discusses the crucial role an HVAC filter plays, guides you in choosing the right air filter for your system, and explains how to locate and replace it.

“Changing your filter can make a world of difference for the overall health, efficiency, and life of your system,” said Josh Elliott, the HVAC training technician at Indianapolis, IN-based Williams Comfort Air.

The Role of an HVAC Filter

Many homeowners misunderstand the actual role of HVAC filters. While they do improve indoor air quality, their primary job is to stop dust, dirt, and other debris from entering the unit to keep the system clean.

Clogged filters restrict airflow, leading to decreased efficiency and potential breakdowns.

How Often Should You Change Your Furnace Filter?

Air filters should be changed about every two or three months. However, the frequency depends on factors such as the type of filter and its efficiency rating. The unit’s owner’s manual will recommend the correct filter type and how often to change it.

Most standard filter packaging states that they last up to 90 days, with “up to” being the key phrase, Elliott said.

“How often you change your filter depends on the type of filter, your environment, and how much dirt is going through the system,” he said. “I recommend checking it every 30 days and changing it as needed. If the color of the filter changes from that nice bright white and you notice some discoloration, it’s time to change it.”


Image of a dirty and clean HVAC air filter

Choosing the Right Air Filter for Your HVAC System

There are several types of furnace filters to choose from, including fiberglass, pleated, HEPA, and electrostatic filters, each offering unique benefits.

If you know where the filter compartment is, turn off your HVAC system, open it up, and remove the filter to check its size and efficiency level, measured by its MERV rating. If you’re not sure where to find the filter and don’t have the owner’s manual handy, search your system type online.

Next, head to the store to buy a new filter. A MERV 8 filter, which is suitable for most homes, costs about $20. Buying in bulk can help you save money.

Finding the Air Filter Compartment

With your new filter in hand, it’s time to locate the filter compartment on your indoor HVAC unit if you haven't already. The compartment is either at the top or bottom of your unit depending on whether you have a downflow or upflow system.

Elliott explains that in an upflow system, the filter compartment is at the bottom, meaning the airflow is pushed through the filter, into the HVAC system, and upward to the home’s air ducts. You’ll notice an arrow at the top of the filter, indicating the correct airflow direction. Make sure it’s pointed toward the furnace.

In a downflow system, air is pushed down through the air filter, into the HVAC system, and to the ducts below. Upflow systems are commonly found in ranch-style homes where the ductwork is in a crawlspace and the supply registers are on the floor. When changing a filter on an upflow system, ensure the arrow is pointing downward toward the unit.

How to Change Your Furnace Filter

Open the air filter compartment, slide the old filter out, and insert the new one. You can tell if a furnace filter needs to be replaced by its color, as a dirty or clogged filter typically appears dark or gray compared to a clean, white filter.

Instead of throwing away your old filter in an indoor trash can, seal it in a bag and dispose of it in an outdoor trash container. This prevents any dust and dirt from escaping and contaminating your home’s air supply.

Your job is now complete! Don’t forget to check your filter about every 30 days to see if it needs to be replaced.

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