Picking out the correct 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 role in keeping its system operating safely, efficiently and for a long time.

A dirty furnace filter loses its effectiveness, enabling potentially harmful particles to move 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 ideal for your needs is not just about keeping your furnace operating efficiently. It’s also about providing good indoor air quality for your household.

The health of your family is important to the heating specialists at Fletcher Plumbing, Heating & AC. We've long been dedicated to improving indoor air quality in Smyrna. Here, we’ve answered common questions about HVAC filters, including that particularly 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 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 recommend examining 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. People who have pets will probably need 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 usually found in the return air duct or blower compartment before the return air goes back into the furnace. This ensures air flowing 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, within the furnace. It's typically housed within 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 the furnace in your home.

Are Air Filters and Furnace Filters the Same Thing?

The easy answer is, yes. In HVAC, a furnace filter and an air filter or AC filter are basically the same. While people might refer to them differently based on the current season— warm or chilly months—they are all filters that clean the air in your home.

They each get rid of dust, allergens, bacteria and other particulates 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 Rating Is Best for Me?

Once you locate your old furnace filter and decide 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 choosing an appropriate MERV rating for your needs.

MERV is short for Minimum Efficiency Reporting Values. The MERV rating indicates the effectiveness of air filters at trapping airborne contaminants. The rating scale ranges from 1 to 20, with higher 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 good indoor air quality without unnecessarily restricting airflow. However, people with specific health conditions may need a a higher MERV rating.

Which Way to Put the Air Filter in a Furnace or AC Unit

Positioning an air filter in a furnace or air conditioner correctly is crucial for the efficient operation of the unit. Air filters are designed to be installed in a specific direction, indicated by an arrow printed 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, it may be helpful to remember that air always moves from the return duct to the heat or cooling source. Therefore, make sure the arrow points in the direction of the furnace or AC.

Many people struggle with which direction to point their air filter. To help remember, consider taking a quick picture 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 point. A handy time to ask about this is during a routine furnace maintenance appointment.

How to Change a Furnace Air Filter

Replacing the filter on your furnace or AC is a simple process. Here is a step-by-step list of how to remove a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Be sure to shut off your furnace before starting the process.
  2. Look for the furnace filter: Typically, the filter is positioned in 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 in the same direction.
  3. Take out the old filter: Be diligent not to knock out any dust or debris.
  4. Record the date: Write down the date you replaced the filter on the new filter's frame. This will make it easier to keep track of when it's time for another replacement.
  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 lock it in the unit.
  7. Turn on your furnace: Once the replacement filter is completely secured, you can turn your furnace back on.

Can a Dirty Air Filter Cause a Furnace Not to Work?

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 conditioner filter is one of the simplest things you can do to keep your system working correctly.