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 function in keeping its system running safely, efficiently and for a long time.

A clogged furnace filter loses its effectiveness, allowing potentially harmful particles to flow through your home. It also limits airflow, which can damage your furnace and shorten its life span.

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

The quality of the air your family breathes is important to the heating specialists at Bell Air Conditioning Inc. We've long worked with an eye on enhancing indoor air quality in Temple/Belton . 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?

When Should I Replace My Furnace Air Filter?

It's vital to replace dirty air filters in a furnace or air conditioner routinely. Dirty filters cause the system to worker harder than it should because it takes more energy to move air through the plugged-up filter.

Officials suggest checking your furnace filter monthly 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. Homeowners who have dogs and cats will very likely need to replace their furnace air filter more often, because an effective 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 usually found in the return air duct or blower compartment before the return air goes back into the furnace. This is so air flowing into the system is filtered before it goes 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 generally housed inside of a slot, frame or cabinet for easy access and replacement. Always refer to your furnace's owner manual for important information about filter location of the furnace in your home.

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 effectively the same. While people might refer to them differently based on the current season— hot or cold—they are all filters that clean the air in your HVAC system.

They each eliminate dust, allergens, bacteria and other particulates from the air that is drawn into the furnace and air conditioning system, ensuring the air distributed throughout your home is clean and safe.

What Are MERV Ratings and What MERV Rating Do I Need?

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 method to do this is by choosing an appropriate MERV rating for your needs.

MERV stands for Minimum Efficiency Reporting Values. The MERV rating calculates the effectiveness of air filters at trapping airborne contaminants. 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 a good balance between having adequate indoor air quality without overly restricting airflow. However, people with some health conditions may need to use a filter with a higher MERV rating.

Where to Insert the Air Filter in a Furnace or Air Conditioner

Putting an air filter in a furnace or air conditioner the proper way is crucial 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 placed in the unit with this arrow pointing at the furnace or AC, which is the direction of the airflow. If you're unsure about the airflow direction, try to remember that air always moves from the return duct to the heat or cooling source. Therefore, be sure that the arrow points in the direction of the furnace or air conditioner.

Many people have difficulty remembering which direction to point their air filter. To help remember, consider snapping a quick photo with your mobile phone after the filter has been correctly 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 point. A great time to inquire about this is during a scheduled furnace maintenance appointment.

How to Change a Furnace Air Filter

Replacing the filter on your furnace or air conditioner is an easy process. Here is a step-by-step rundown of how to remove a dirty air filter and exchange it for a new one:

  1. Turn off your furnace: Be sure to turn off your furnace before starting up the process.
  2. Look for the furnace filter: Typically, the filter is positioned inside the furnace or in the air return vent. Make a mental note or write down which direction the arrow points on the filter, because you’ll want the arrow on the clean filter to point in the same direction.
  3. Slide out the old filter: Be mindful not to knock out any dust or dirt.
  4. Document the date: Write down the date you changed filters on the new filter's frame. This will make it easier to 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 nicely and close any latches or clips that hold it in the compartment.
  7. Turn on your furnace: Once the clean filter is properly installed, you can turn your furnace back on.

Will a Dirty Air Filter Damage My Furnace?

The short answer is, yes, a dirty air filter can cause a furnace to stop working or decrease its lifespan. Changing your furnace or AC filter is one of the best things you can do to keep your system operating effectively.