Choosing 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.

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

Making sure your furnace uses a clean filter that is appropriate for your needs is not just about keeping your furnace working efficiently. It’s also about creating healthy indoor air quality for your household.

The health of your family is important to the HVAC specialists at Ohler & Holzhauer Inc.. We've long focused on bettering indoor air quality in Port Clinton. Here, we’ve answered frequent questions about HVAC filters, including that especially 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 critical to replace dirty air filters in a furnace or air conditioner routinely. Dirty filters cause the system to worker harder than it should because it takes extra effort 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 be gray or black from dirt or dust. Homeowners who have dogs and cats will very likely need to replace their furnace air filter more often, because a quality air filter will trap pet hair circulating in a home.

Where Is the Air Filter in My Furnace?

In general, a furnace air filter is commonly installed in the return air duct or blower compartment before the return air reaches the furnace. This makes sure 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 typically housed inside of a slot, frame or cabinet for convenient access and replacement. Always refer to your furnace's owner manual for details regarding filter location of your particular brand and model of furnace.

Is a Furnace Filter the Same as an Air Filter?

The easy answer is, yes. In HVAC, a furnace filter and an air filter or air conditioner filter are essentially identical. 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 remove dust, allergens, bacteria and other particulates from the air that is drawn into the furnace and air conditioning system, making certain the air distributed throughout your home is clean and safe.

What Is a MERV Rating and What MERV Rating Should I Have?

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

MERV stands for Minimum Efficiency Reporting Values. The MERV rating calculates the effectiveness of air filters at trapping airborne particles. The rating scale ranges from 1 to 20, with higher numbers indicating the power 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 might need to use a filter 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 properly is necessary for the efficient operation of the heating or cooling system. Air filters have a specific direction, indicated by an arrow printed on the side of the filter frame. The filter should be installed with this arrow pointing at the furnace or air conditioning unit, 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 certain the arrow points toward the furnace or air conditioning unit.

Many people struggle with which direction to point their 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 go. A perfect time to inquire about this is during a regular furnace maintenance call.

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 rundown of how to remove a dirty air filter and replace it with a new one:

  1. Turn off your furnace: Be sure to shut off your furnace before starting up the process.
  2. Look for the furnace filter: Typically, the filter is positioned in the furnace or in the air return vent. Make a mental note or write down which direction the arrow points on the filter, because you’ll want the arrow on the replacement filter to point in the same direction.
  3. Remove the old filter: Be mindful not to knock out any dust or dirt.
  4. Document 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 the next change.
  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 correctly and close any latches or clips that secure it in place.
  7. Turn on your furnace: Once the new filter is properly installed, you can turn your furnace back on.

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

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