Picking out the right furnace filter and changing it when it becomes 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 running safely, efficiently and for a long time.

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

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

The quality of the air your family breathes is important to the heating specialists at Gee & Missler Heating & Air Conditioning. We've long been dedicated to bettering indoor air quality in Wyandotte. Here, we’ve answered common questions about HVAC filters, including that very 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 critical 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 effort to move air through the plugged-up filter.

Officials suggest examining your furnace filter every month 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 pets that shed will probably have to replace their furnace air filter more often, because a good 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 installed in the return air duct or blower compartment before the return air gets to the furnace. This ensures air entering the system is filtered before it moves 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, inside the furnace. It's usually housed within a slot, frame or cabinet for easy access and replacement. Always refer to your furnace's owner manual for details concerning filter location of your furnace.

Is a Furnace Filter the Same as an 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 may call them different things based on the current season— summer or winter—they are all filters that clean the air in your residence.

They each get rid of dust, allergens, bacteria and other airborne debris 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 a MERV Rating and What MERV Rating Do I Need?

Once you locate your old furnace filter and determine when it should be replaced, it’s time to select a replacement. That means determining the level of filtration that you need. One approach to this is by selecting an appropriate MERV rating for your needs.

MERV stands for Minimum Efficiency Reporting Values. The MERV rating indicates 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 appropriate balance between having adequate indoor air quality without unnecessarily restricting airflow. However, people with some health conditions may need a a higher MERV rating.

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

Positioning an air filter in a furnace or air conditioner the proper way is important 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 put in with this arrow pointing toward the furnace or air conditioner, 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, make certain the arrow points at the furnace or air conditioning unit.

Many people have difficulty remembering which direction to point an air filter. To help remember, consider snapping a quick photo with your cellular 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 go. A handy time to inquire about this is during a regular furnace maintenance visit.

How to Change a Furnace Air Filter

Switching out the filter on your furnace or AC is an 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. 1. Turn off your furnace: Make sure to switch off your furnace before starting up the process.
  2. Find the furnace filter: Typically, the filter is positioned within 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. Take out the old filter: Be careful not to knock out any dust or dirt.
  4. Note the date: Write down the date you replaced the filter on the new filter's frame. This will help you keep track of when it's time for another replacement.
  5. Put in new filter: Put in the new filter with the arrow pointing in the direction of 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 correctly and close any latches or clips that secure it in place.
  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 stop working or limit its lifespan. Changing your furnace or air conditioning filter is one of the easiest things you can do to keep your system operating effectively.