Selecting the proper 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 role in keeping its system running safely, efficiently and for a long time.

A clogged furnace filter loses its effectiveness, permitting potentially harmful particles to move through your home. It also restricts 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 providing healthy indoor air quality for your household.

Your health is important to the heating specialists at North Mechanical Heating and Cooling. We've long worked with an eye on bettering indoor air quality in Payson. 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?

When to Replace the Air Filter in Your Furnace

Experts stress it's vital to replace dirty air filters in a furnace or air conditioner periodically. Dirty filters cause the system to worker harder than it should because it takes extra effort to pull air through the plugged-up filter.

Officials recommend inspecting your furnace filter every 30 days and replacing it if it’s dirty. You’ll know if your filter needs changing because it will be gray or black from dirt or dust. People who have pets will very likely 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 commonly located in the return air duct or blower compartment before the return air goes back into the furnace. This ensures air entering 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 within a slot, frame or cabinet for easy access and replacement. Always refer to your furnace's owner manual for information concerning filter location of the furnace in your home.

Are Air Filters and Furnace Filters the Same Thing?

The simple answer is, yes. In HVAC, a furnace filter and an air filter or air conditioner filter are effectively 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 residence.

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, ensuring the air distributed throughout your home is clean and safe.

What Are MERV Ratings and What MERV Rating Should I Have?

Once you locate your old furnace filter and decide when it should be substituted for a clean one, it’s time to choose a replacement. That means deciding on the level of filtration that you need. One method to do this is by choosing 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 contaminants. The rating scale ranges from 1 to 20, with greater numbers indicating a greater ability to filter tinier particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having good indoor air quality without unnecessarily restricting airflow. However, people with certain 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 the proper way is necessary for the efficient operation of the system. Air filters are supposed to face a specific direction, indicated by an arrow printed 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 unsure about the airflow direction, try to remember that air always moves from the return duct to the heat or cooling source. Therefore, make certain the arrow points toward the furnace or AC.

Many people have difficulty remembering which direction to face an 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 go. A handy time to do this is during a routine furnace maintenance visit.

Changing Your Furnace's Air Filter

Replacing the filter on your furnace or air conditioning system is a quick and easy process. Here is a step-by-step list of how to take out a dirty air filter and replace it with a new one:

  1. Turn off your furnace: Be 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. Make note of which direction the arrow points on the filter, because you’ll want the arrow on the replacement filter to point similarly.
  3. Remove the old filter: Be careful not to knock out any dust or dirt.
  4. Record the date: Write down the date you replaced the filter on the new filter's frame. This will help you keep track of when it's time for you to change it again.
  5. Slide 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 correctly and close any latches or clips that hold it in the unit.
  7. Turn on your furnace: Once the clean filter is properly secured, you can turn your furnace back on.

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

The short answer is, yes, a dirty air filter can cause a furnace to quit working or reduce its lifespan. Changing your furnace or air conditioning filter is one of the easiest things you can do to keep your system running effectively.