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

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

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

Your health is important to the HVAC specialists at Air Masters Heating & Cooling. We've long focused on bettering indoor air quality in Port Orchard. Here, we’ve answered frequent 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

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

Officials suggest checking your furnace filter every 30 days and replacing it if it’s dirty. You’ll know if your filter needs changing because it will coated with dirt or dust. People who have pets that shed will probably need to replace their furnace air filter more often, because an effective 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 commonly located in the return air duct or blower compartment before the return air reaches the furnace. This makes sure air being pulled into the system is filtered before it moves through the furnace components and is heated.

Depending on the furnace brand, the filter may be found on the right, left, bottom or in some cases, inside the furnace. It's typically housed within a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for facts about filter location of your particular brand and model of furnace.

Are Air Filters and Furnace Filters the Same Thing?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or air conditioner filter are effectively the same thing. While people may call them different things based on the current season— warm or chilly months—they are all filters that clean the air in your HVAC system.

They each get rid of dust, allergens, bacteria and other contaminants from the air that is drawn into the furnace and air conditioning system, ensuring the air circulating throughout your home is clean and safe.

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

Once you locate your old furnace filter and figure out when it should be changed, it’s time to pick a replacement. That means picking the level of filtration that you need. One approach to this is by picking 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 molecules. The rating scale ranges from 1 to 20, with higher numbers indicating the power to filter smaller particles.

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

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

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 particular direction, indicated by an arrow printed on the side of the filter frame. The filter should be installed with this arrow pointing at the furnace or air conditioner, which is the direction of the airflow. If you're unsure about the airflow direction, remember that air always moves from the return duct and then to the heat or cooling source. Therefore, be sure that the arrow points toward the furnace or air conditioner.

Many people struggle with which direction to point their system's air filter. To help remember, consider taking a picture with your cell 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 perfect time to do this is during a scheduled furnace maintenance call.

Changing Your Furnace's Air Filter

Switching out 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 take out a dirty air filter and replace it with a new one:

  1. Turn off your furnace: Make a point to shut off your furnace before starting up the process.
  2. Locate the furnace filter: Typically, the filter is positioned inside 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 new filter to point similarly.
  3. Slide out the old filter: Be careful not to knock out any dust or debris.
  4. Document the date: Write down the date you changed filters on the new filter's frame. This will help your family keep track of when it's time for another replacement.
  5. Put in 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 your last filter.
  6. Secure the filter: Make sure the new filter fits correctly and close any latches or clips that hold it in place.
  7. Turn on your furnace: Once the new filter is safely 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 cease 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 working effectively.