Selecting the ideal 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 critical role in keeping its system working safely, efficiently and for a long time.

An overused furnace filter loses its effectiveness, permitting potentially harmful particles to flow through your home. It also restricts airflow, which can damage your furnace and decrease its life span.

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

The quality of the air your family breathes is important to the heating and cooling specialists at Farris Heating & Air. We've long worked with an eye on improving indoor air quality in Bartlesville. Here, we’ve answered frequent questions about HVAC filters, including that particularly 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

Experts stress it's important to replace dirty air filters in a furnace or air conditioner routinely. Soiled filters cause the system to worker harder than it should because it takes extra work to force air through the plugged-up filter.

Officials advise examining 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 coated with dirt or dust. Those who have dogs and cats will probably need to replace their furnace air filter more often, because a quality air filter will trap pet hair circulating in a home.

Where Is the Air Filter in My Furnace?

In general, a furnace air filter is normally found in the return air duct or blower compartment before the return air goes back into the furnace. This makes sure air flowing into the system is filtered before it moves through the furnace components and is heated.

Depending on the furnace brand, the filter may be located on the right, left, bottom or in some cases, inside the furnace. It's usually housed in a slot, frame or cabinet for convenient access and replacement. Always refer to your furnace's owner manual for important information regarding filter location of your particular brand and model of furnace.

Is My Furnace Filter Just a Type of Air Filter?

The easy answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are effectively the same. 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 home.

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

What Is the MERV Rating System and What MERV Rating Should I Have?

Once you find your old furnace filter and decide when it should be substituted for a clean one, it’s time to choose a replacement. That means determining the level of filtration that you need. One approach to this is by choosing an appropriate MERV rating for your needs.

MERV stands for Minimum Efficiency Reporting Values. The MERV rating measures the effectiveness of air filters at trapping airborne contaminants. The rating scale ranges from 1 to 20, with bigger numbers indicating the power to filter smaller particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having good indoor air quality without needlessly restricting airflow. However, people with some health conditions may need to use a filter with a higher MERV rating.

How to Place the Air Filter in a Furnace or AC Unit

Putting an air filter in a furnace or air conditioner the proper way is necessary for the efficient operation of the unit. Air filters are designed to be installed in a specific direction, indicated by an arrow located on the side of the filter frame. The filter should be installed with this arrow pointing in the direction of the furnace or AC, which is the direction of the airflow. If you're doubtful about the airflow direction, try to remember that air always moves from the return duct and then to the heat or cooling source. Therefore, be sure that the arrow points at the furnace or AC.

Many people are confused by which direction to point their air filter. To help remember, consider taking a quick picture with your mobile 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 call.

How to Change a Furnace Air Filter

Switching out the filter on your furnace or AC is a quick and easy process. Here is a step-by-step list of how to take out a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Make a point to shut off your furnace before starting the process.
  2. Locate the furnace filter: Typically, the filter is found in the furnace or in the air return vent. Make note of which direction the arrow points on the filter, because you’ll want the arrow on the replacement filter to point similarly.
  3. Remove the old filter: Be diligent not to knock out any dust or particles.
  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. Insert new filter: Put in the new filter with the arrow pointing toward the furnace, which is the direction of airflow and should be the same direction the arrow pointed on the dirty filter you just removed.
  6. Secure the filter: Make sure the new filter fits securely and close any latches or clips that secure it in the unit.
  7. Turn on your furnace: Once the new filter is completely installed, you can turn your furnace back on.

Will a Dirty Air Filter Cause a Furnace Not to Work?

The short answer is, yes, a dirty air filter can cause a furnace to cease working or shorten its lifespan. Changing your furnace or air conditioning filter is one of the simplest things you can do to keep your system working efficiently.