Picking out the proper furnace filter and changing it when it gets 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 operating 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 slows airflow, which can damage your furnace and decrease its life span.

Ensuring your furnace uses a clean filter that is appropriate for your needs is not only about keeping your furnace operating efficiently. It’s also about creating healthy indoor air quality for your household.

Your health is important to the heating professionals at E.B. Air. We've long worked with an eye on bettering indoor air quality in East Bernard. Here, we’ve answered frequent 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 critical 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 effort to force air through the plugged-up filter.

Officials advise examining your furnace filter monthly and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will filled with dirt or dust. People who have pets that shed will very likely have 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 usually installed in the return air duct or blower compartment before the return air gets to the furnace. This makes sure air being pulled into the system is filtered before it passes through the furnace components and is heated.

Depending on the furnace model, the filter may be found 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 regarding 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 AC filter are essentially identical. 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 remove 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 MERV Rating Do I Need?

Once you find your old furnace filter and figure out when it should be changed, it’s time to choose a replacement. That means picking the level of filtration that you need. One way to do that is by selecting an appropriate MERV rating for your needs.

MERV is an abbreviation 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 higher numbers indicating enhanced capabilities to filter small particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having good indoor air quality without overly restricting airflow. However, people with certain health conditions might need to purchase a filters with 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 the proper way is necessary for the efficient operation of the system. Air filters are designed to be installed in a specific direction, indicated by an arrow written on the side of the filter frame. The filter should be placed in the unit with this arrow pointing toward the furnace or air conditioner, 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 and then to the heat or cooling source. Therefore, make sure the arrow points at the furnace or AC.

Many people are confused by which direction to point their system's air filter. To help remember, consider snapping a quick photo 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 rundown of how to take out a dirty air filter and swap it for a new one:

  1. 1. Turn off your furnace: Be sure to switch off your furnace before starting the process.
  2. Locate the furnace filter: Typically, the filter is located in 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 new filter to point similarly.
  3. Slide out the old filter: Be careful not to knock out any dust or particles.
  4. Document 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 another replacement.
  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 old filter you are replacing.
  6. Secure the filter: Make sure the new filter fits correctly and close any latches or clips that secure it in the compartment.
  7. Turn on your furnace: Once the replacement filter is safely 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 reduce its lifespan. Changing your furnace or AC filter is one of the easiest things you can do to keep your system operating efficiently.