Choosing 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 crucial part in keeping its system working safely, efficiently and for a long time.

An overused furnace filter loses its effectiveness, permitting potentially harmful particles to move 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 ideal for your needs is not only about keeping your furnace working efficiently. It’s also about delivering excellent indoor air quality for your home.

Your health is important to the heating pros at Fletcher Plumbing, Heating & AC. We've long been dedicated to improving indoor air quality in Smyrna. 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 is critical to replace dirty air filters in a furnace or air conditioner regularly. 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 monthly and replacing it if it’s dirty. You’ll know if it is dirty because it will coated with dirt or dust. Homeowners who have pets will probably have to replace their furnace air filter more often, because an effective air filter will trap pet hair circulating in a home.

Locating Your Furnace's Air Filter

In general, a furnace air filter is normally found in the return air duct or blower compartment before the return air gets to 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 positioned on the right, left, bottom or in some cases, on the inside of the furnace. It's usually housed inside of a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for information about filter location of your furnace.

Are Air Filters and Furnace Filters the Same Thing?

The easy answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are basically 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 eliminate dust, allergens, bacteria and other contaminants from the air that is drawn into the furnace and air conditioning system, making sure the air flowing through 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 figure out when it should be substituted for a clean one, it’s time to pick a replacement. That means picking the level of filtration that you need. One way to do that is by picking an appropriate MERV rating for your needs.

MERV is short 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 greater numbers indicating enhanced capabilities 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 could need to purchase a filters with a higher MERV rating.

Which Way to Put the Air Filter in a Furnace or Air Conditioning System

Positioning an air filter in a furnace or air conditioner properly is crucial for the efficient operation of the heating or cooling system. Air filters have a certain direction, indicated by an arrow printed on the side of the filter frame. The filter should be installed with this arrow pointing toward the furnace or air conditioning unit, which is the direction of the airflow. If you're unsure about the airflow direction, remember that air always moves from the return duct to the heat or cooling source. Therefore, make certain the arrow points in the direction of the furnace or air conditioner.

Many people have difficulty remembering which direction to install their air filter. To help remember, consider snapping a quick photo with your cellular 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 be installed. A handy time to do this is during a regular furnace maintenance appointment.

How to Change a Furnace Air Filter

Switching out the filter on your furnace or AC is a simple process. Here is a step-by-step breakdown of how to retreive a dirty air filter and exchange it for a new one:

  1. Turn off your furnace: Make sure to turn 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 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 similarly.
  3. Take out the old filter: Be diligent not to knock out any dust or particles.
  4. Document the date: Write down the date you changed filters on the new filter's frame. This will help you keep track of when it's time for another replacement.
  5. Insert 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 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 clean filter is completely secured, you can turn your furnace back on.

Can a Dirty Air Filter Cause Problems for a Furnace?

The shortest answer is, yes, a dirty air filter can cause a furnace to quit working or decrease its lifespan. Changing your furnace or air conditioning filter is one of the simplest things you can do to keep your system working correctly.