Selecting the ideal 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 vital function in keeping its system working safely, efficiently and for a long time.

A dirty furnace filter loses its effectiveness, allowing potentially harmful particles to circulate 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 merely about keeping your furnace working efficiently. It’s also about delivering good indoor air quality for your residence.

The quality of the air your family breathes is important to the heating pros at Cooler Tymes LLC. We've long worked with an eye on enhancing indoor air quality in Litchfield Park. Here, we’ve answered frequent questions about HVAC filters, including that very 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 vital to replace dirty air filters in a furnace or air conditioner regularly. Dirty filters cause the system to worker harder than it should because it takes extra work to force air through the plugged-up filter.

Officials suggest inspecting your furnace filter every 30 days 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. Those who have pets that shed will likely need 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 normally found in the return air duct or blower compartment before the return air reaches the furnace. This ensures air entering the system is filtered before it moves through the furnace components and is heated.

Depending on the furnace model, the filter may be located on the right, left, bottom or in some cases, within the furnace. It's typically housed in a slot, frame or cabinet for convenient access and replacement. Always refer to your furnace's owner manual for information about filter location of the furnace in your home.

Are Air Filters and Furnace Filters the Same Thing?

The easy answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are essentially the same thing. While people might refer to them differently based on the current season— summer or winter—they are all filters that clean the air in your home.

They each eliminate dust, allergens, bacteria and other contaminants 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 Is the MERV Rating System and What Rating Is Best for Me?

Once you find your old furnace filter and figure out when it should be replaced, it’s time to select 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 measures the effectiveness of air filters at trapping airborne contaminants. The rating scale ranges from 1 to 20, with bigger numbers indicating enhanced capabilities to filter smaller particles.

Experts say a filter with a MERV rating between 8 and 13 offers a good balance between having healthy indoor air quality without unnecessarily restricting airflow. However, people with some health conditions could need to purchase a filters with a higher MERV rating.

Where to Insert the Air Filter in a Furnace or Air Conditioning System

Putting an air filter in a furnace or air conditioner properly is crucial for the efficient operation of the unit. Air filters have a particular direction, indicated by an arrow located on the side of the filter frame. The filter should be installed with this arrow pointing in the direction of the furnace or air conditioning unit, which is the direction of the airflow. If you're unsure about the airflow direction, remember that air always moves from the return duct and then to the heat or cooling source. Therefore, make sure the arrow points at the furnace or AC.

Many people struggle with which direction to face an air filter. To help remember, consider taking a quick picture with your cellular 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 point. A great time to ask about this is during a scheduled furnace maintenance visit.

Changing Your Furnace's Air Filter

Changing the filter on your furnace or air conditioning system is a simple process. Here is a step-by-step rundown of how to retreive a dirty air filter and replace it with a new one:

  1. Turn off your furnace: Make 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 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 replaced the filter on the new filter's frame. This will make it easier to 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 the old filter you are replacing.
  6. Secure the filter: Make sure the new filter fits nicely and close any latches or clips that secure it in place.
  7. Turn on your furnace: Once the new filter is completely secured, 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 simplest things you can do to keep your system operating effectively.