Choosing the right furnace filter and changing it when it is dirty is as important to your HVAC system as changing the oil is to your car. Each plays a vital role in keeping its system running safely, efficiently and for a long time.

A dirty furnace filter loses its effectiveness, permitting potentially harmful particles to move through your home. It also limits airflow, which can damage your furnace and decrease its life span.

Making sure your furnace uses a clean filter that is suitable for your needs is not only about keeping your furnace working efficiently. It’s also about delivering good indoor air quality for your home.

The health of your family is important to the heating pros at B&D Air Conditioning. We've long been dedicated to bettering indoor air quality in Safford. Here, we’ve answered common questions about HVAC filters, including that especially tricky question of what direction do you point a filter in your furnace or air conditioner?

How Often to Replace the Air Filter in a Furnace

It's important to replace dirty air filters in a furnace or air conditioner regularly. Dirty filters cause the system to worker harder than it should because it takes extra work to move air through the plugged-up filter.

Officials suggest inspecting your furnace filter every 30 days and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will be gray or black from dirt or dust. People who have pets will likely want to replace their furnace air filter more often, because a good air filter will trap pet hair circulating in a home.

How to Find the Furnace's Air Filter

In general, a furnace air filter is usually found in the return air duct or blower compartment before the return air gets to the furnace. This is so air entering the system is filtered before it goes through the furnace components and is heated.

Depending on the type of furnace, the filter may be located on the right, left, bottom or in some cases, on the inside of the furnace. It's generally housed in a slot, frame or cabinet for convenient access and replacement. Always refer to your furnace's owner manual for details concerning filter location of your furnace.

Is My Furnace Filter Just a Type of Air Filter?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are essentially identical. While they might be called different things based on the current season— summer or winter—they are all filters that clean the air in your HVAC system.

They each eliminate dust, allergens, bacteria and other contaminants from the air that is drawn into the furnace and air conditioning system, making sure the air circulating throughout your home is clean and safe.

What Is a MERV Rating and What Rating Is Best for Me?

Once you track down your old furnace filter and decide when it should be replaced, it’s time to pick a replacement. That means determining the level of filtration that you need. One way to do that is by choosing an appropriate MERV rating for your needs.

MERV is short for Minimum Efficiency Reporting Values. The MERV rating calculates the effectiveness of air filters at trapping airborne particles. The rating scale ranges from 1 to 20, with bigger numbers indicating a greater ability to filter small particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having adequate indoor air quality without unnecessarily restricting airflow. However, people with specific health conditions could need a a higher MERV rating.

Which Way to Put the Air Filter in a Furnace or Air Conditioner

Putting an air filter in a furnace or air conditioner correctly is necessary for the efficient operation of the system. Air filters have a particular direction, indicated by an arrow written on the side of the filter frame. The filter should be installed with this arrow pointing toward the furnace or air conditioning unit, which is the direction of the airflow. If you're not sure about the airflow direction, try to remember that air always moves from the return duct towards the heat or cooling source. Therefore, make sure the arrow points in the direction of the furnace or air conditioning unit.

Many people have difficulty remembering which direction to install their air filter. To help remember, consider snapping a quick photo with your cell phone after the filter has been accurately installed by a professional. Or, you also could ask a technician to use a marker to write on the outside of your furnace which direction the filter should go. A handy time to inquire about this is during a routine furnace maintenance visit.

How to Replace Your Furnace Air Filter

Changing the filter on your furnace or air conditioning system is a quick and easy process. Here is a step-by-step breakdown of how to retreive a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Make a point to turn off your furnace before starting the process.
  2. Locate the furnace filter: Typically, the filter is positioned in the furnace or in the air return vent. Take note of which direction the arrow points on the filter, because you’ll want the arrow on the clean filter to point similarly.
  3. Slide out the old filter: Be mindful not to knock out any dust or debris.
  4. Record the date: Write down the date of replacement on the new filter's frame. This will help your family keep track of when it's time for you to change it again.
  5. Put in new filter: Put in the new filter with the arrow pointing at the furnace, which is the direction of airflow and should be the same direction the arrow pointed on your last filter.
  6. Secure the filter: Make sure the new filter fits correctly and close any latches or clips that hold it in the compartment.
  7. Turn on your furnace: Once the replacement filter is safely secured, you can turn your furnace back on.

Will a Dirty Air Filter Damage My Furnace?

The simple answer is, yes, a dirty air filter can cause a furnace to quit working or shorten its lifespan. Changing your furnace or air conditioning filter is one of the best things you can do to keep your system running correctly.