Picking out 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 critical function in keeping its system running 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 shorten its life span.

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

The health of your family is important to the heating professionals at Home Comfort Heating & Air. We've long worked with an eye on enhancing indoor air quality in Elk River. 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?

When Should I Replace My Furnace Air Filter?

It's important 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 suggest inspecting your furnace filter every month and replacing it if it’s dirty. You’ll know if your filter needs changing because it will coated with dirt or dust. Homeowners who have dogs and cats will very likely have to replace their furnace air filter more often, because a good air filter will trap pet hair circulating in a home.

Locating Your Furnace's Air Filter

In general, a furnace air filter is normally located in the return air duct or blower compartment before the return air gets to the furnace. This ensures air flowing into the system is filtered before it passes through the furnace components and is heated.

Depending on the type of furnace, the filter may be positioned on the right, left, bottom or in some cases, within the furnace. It's usually housed inside of a slot, frame or cabinet for easy access and replacement. Always refer to your furnace's owner manual for details about filter location of your furnace.

Are Air Filters and Furnace Filters the Same Thing?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are effectively 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 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, making sure the air circulating throughout your home is clean and safe.

What Are MERV Ratings and What Rating Is Best for Me?

Once you find your old furnace filter and figure out when it should be changed, it’s time to choose a replacement. That means deciding on the level of filtration that you need. One approach to this is by selecting 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 higher numbers indicating the power to filter smaller particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having adequate indoor air quality without overly restricting airflow. However, people with some health conditions might need a a higher MERV rating.

Where to Insert the Air Filter in a Furnace or Air Conditioner

Putting an air filter in a furnace or air conditioner the proper way is important for the efficient operation of the heating or cooling system. Air filters are supposed to face a certain direction, indicated by an arrow located on the side of the filter frame. The filter should be placed in the unit with this arrow pointing at the furnace or air conditioner, which is the direction of the airflow. If you're not sure about the airflow direction, it may be helpful to remember that air always moves from the return duct towards the heat or cooling source. Therefore, be sure that the arrow points toward the furnace or air conditioning unit.

Many people struggle with which direction to point their system's air filter. To help remember, consider taking a picture with your cell phone after the filter has been properly 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 perfect time to ask about this is during a routine furnace maintenance call.

How to Replace Your Furnace Air Filter

Changing the filter on your furnace or AC 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. Locate the furnace filter: Typically, the filter is positioned 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 mindful not to knock out any dust or dirt.
  4. Record the date: Write down the date you changed filters 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 in the direction of 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 lock it in the unit.
  7. Turn on your furnace: Once the clean filter is properly installed, you can turn your furnace back on.

Will a Dirty Air Filter Damage My Furnace?

The short answer is, yes, a dirty air filter can cause a furnace to stop working or shorten its lifespan. Changing your furnace or AC filter is one of the best things you can do to keep your system running efficiently.