Picking out the right furnace filter and changing it when it is dirty is as important to your HVAC system as changing the oil is to your car. Each plays a critical role in keeping its system operating safely, efficiently and for a long time.

A clogged furnace filter loses its effectiveness, permitting potentially harmful particles to flow through your home. It also restricts airflow, which can damage your furnace and shorten its life span.

Ensuring your furnace uses a clean filter that is suitable for your needs is not just about keeping your furnace working efficiently. It’s also about providing good indoor air quality for your residence.

The health of your family is important to the heating and cooling pros at Willco Air Conditioning, Refrigeration & Heating Inc.. We've long worked with an eye on enhancing indoor air quality in Branchville. 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?

When Should I Replace My Furnace Air Filter?

It's important to replace dirty air filters in a furnace or air conditioner regularly. Soiled filters cause the system to worker harder than it should because it takes extra work to force 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 the filter needs to be changed because it will be gray or black from dirt or dust. Those who have pets that shed will likely have to replace their furnace air filter more often, because a quality air filter will trap pet hair circulating in a home.

Locating Your Furnace's Air Filter

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

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

Is a Furnace Filter the Same as an Air Filter?

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

They each eliminate dust, allergens, bacteria and other particulates from the air that is drawn into the furnace and air conditioning system, making sure the air flowing through your home is clean and safe.

What Are MERV Ratings and What MERV Rating Do I Need?

Once you track down your old furnace filter and decide when it should be changed, it’s time to pick a replacement. That means deciding on the level of filtration that you need. One way to do that is by picking 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 molecules. 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 an ideal balance between having healthy indoor air quality without overly restricting airflow. However, people with certain 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

Positioning 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 specific direction, indicated by an arrow located on the side of the filter frame. The filter should be put in with this arrow pointing at the furnace or air conditioning unit, which is the direction of the airflow. If you're unsure 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, make certain the arrow points toward the furnace or air conditioner.

Many people have difficulty remembering which direction to point 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 point. A great time to inquire about this is during a regular furnace maintenance visit.

How to Change a Furnace Air Filter

Switching out the filter on your furnace or air conditioning system is a simple process. Here is a step-by-step breakdown of how to remove a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Be sure to switch off your furnace before starting the process.
  2. Locate the furnace filter: Typically, the filter is positioned inside 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 replacement filter to point similarly.
  3. Slide out the old filter: Be diligent not to knock out any dust or dirt.
  4. Note the date: Write down the date you replaced the filter on the new filter's frame. This will make it easier to keep track of when it's time for the next change.
  5. Slide 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 secure it in the compartment.
  7. Turn on your furnace: Once the new filter is properly in place, you can turn your furnace back on.

Will a Dirty Air Filter Cause Problems for a 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 air conditioning filter is one of the simplest things you can do to keep your system working correctly.