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

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

Making certain your furnace uses a clean filter that is appropriate for your needs is not just about keeping your furnace operating efficiently. It’s also about delivering good indoor air quality for your home.

Your health is important to the HVAC professionals at Assured Appliance & Heating & Air. We've long worked with an eye on bettering indoor air quality in Genoa. Here, we’ve answered frequent 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

Experts stress it's important 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 more energy to pull air through the plugged-up filter.

Officials suggest examining your furnace filter every month and replacing it if it’s dirty. You’ll know if it is dirty because it will filled with dirt or dust. Homeowners who have dogs and cats will very likely want 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 normally found in the return air duct or blower compartment before the return air reaches the furnace. This is so air being pulled into the system is filtered before it goes 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 convenient access and replacement. Always refer to your furnace's owner manual for facts about 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 AC 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 residence.

They each get rid of dust, allergens, bacteria and other particulates 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 track down your old furnace filter and determine when it should be substituted for a clean one, 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 measures the effectiveness of air filters at trapping airborne contaminants. The rating scale ranges from 1 to 20, with greater numbers indicating the power to filter tinier 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 could need to use a filter with a higher MERV rating.

How to Place the Air Filter in a Furnace or Air Conditioner

Installing an air filter in a furnace or air conditioner the proper way is necessary for the efficient operation of the system. Air filters are designed to be installed in a particular direction, indicated by an arrow located on the side of the filter frame. The filter should be installed 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, be sure that the arrow points in the direction of the furnace or AC.

Many people struggle with which direction to point an air filter. To help remember, consider taking a quick 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 inquire about this is during a scheduled furnace maintenance appointment.

How to Replace Your Furnace Air Filter

Replacing the filter on your furnace or air conditioner is an easy process. Here is a step-by-step breakdown of how to remove a dirty air filter and replace it with a new one:

  1. Turn off your furnace: Be sure to switch off your furnace before starting up the process.
  2. Locate the furnace filter: Typically, the filter is found 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 clean filter to point the same way.
  3. Take out the old filter: Be careful not to knock out any dust or dirt.
  4. Note 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 you to change it again.
  5. Put in 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 securely and close any latches or clips that lock it in place.
  7. Turn on your furnace: Once the new filter is completely in place, you can turn your furnace back on.

Will a Dirty Air Filter Cause Problems for a Furnace?

The shortest answer is, yes, a dirty air filter can cause a furnace to stop working or limit its lifespan. Changing your furnace or air conditioner filter is one of the best things you can do to keep your system operating effectively.