Selecting the right 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 crucial role in keeping its system working 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 slows airflow, which can damage your furnace and decrease its life span.

Ensuring 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 delivering healthy indoor air quality for your home.

Your health is important to the HVAC specialists at Ameri-Tec. We've long worked with an eye on enhancing indoor air quality in Narvon. 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

It's critical to replace dirty air filters in a furnace or air conditioner regularly. Dirt-clogged 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 every 30 days and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will be gray or black from dirt or dust. Those who have pets that shed will probably need to replace their furnace air filter more often, because a good 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 installed 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 located on the right, left, bottom or in some cases, within the furnace. It's generally housed in a slot, frame or cabinet for easy access and replacement. Always refer to your furnace's owner manual for important information concerning filter location of your particular brand and model of 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 essentially the same. While they might be called 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 airborne debris from the air that is drawn into the furnace and air conditioning system, making sure the air distributed throughout your home is clean and safe.

What Is the MERV Rating System and What Rating Is Best for Me?

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

MERV is an abbreviation 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 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 healthy indoor air quality without needlessly restricting airflow. However, people with certain health conditions may need to use a filter with a higher MERV rating.

How to Place the Air Filter in a Furnace or Air Conditioning System

Installing an air filter in a furnace or air conditioner properly is important for the efficient operation of the heating or cooling system. 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 toward the furnace or AC, which is the direction of the airflow. If you're unsure about the airflow direction, try to remember that air always moves from the return duct towards the heat or cooling source. Therefore, make sure the arrow points in the direction of the furnace or air conditioning unit.

Many people are confused by which direction to face their air filter. To help remember, consider snapping a quick photo with your cell 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 perfect time to ask about this is during a regular furnace maintenance appointment.

Changing Your Furnace's Air Filter

Switching out the filter on your furnace or air conditioning system is an easy process. Here is a step-by-step list of how to take out 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 up the process.
  2. Look for the furnace filter: Typically, the filter is found 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. Slide out the old filter: Be diligent not to knock out any dust or particles.
  4. Document the date: Write down the date you replaced the filter on the new filter's frame. This will help your family keep track of when it's time for the next change.
  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 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 safely installed, you can turn your furnace back on.

Will a Dirty Air Filter Damage My Furnace?

The simple answer is, yes, a dirty air filter can cause a furnace to cease working or shorten its lifespan. Changing your furnace or AC filter is one of the simplest things you can do to keep your system working effectively.