Choosing the ideal 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 vital part in keeping its system running safely, efficiently and for a long time.

A dirty furnace filter loses its effectiveness, allowing potentially harmful particles to flow 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 just about keeping your furnace running efficiently. It’s also about delivering excellent indoor air quality for your residence.

The health of your family is important to the HVAC specialists at Fal-Ken Heating & Cooling Corporation. We've long been dedicated to improving indoor air quality in Holbrook. 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 to Replace the Air Filter in Your 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 recommend examining your furnace filter monthly 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 have to replace their furnace air filter more often, because a quality 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 commonly located in the return air duct or blower compartment before the return air goes back into the furnace. This is so air entering the system is filtered before it goes through the furnace components and is heated.

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

Is My Furnace Filter Just a Type of Air Filter?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or AC filter are basically the same. While people may call them different things based on the current season— summer or winter—they are all filters that clean the air in your home.

They each remove dust, allergens, bacteria and other contaminants 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 Is the MERV Rating System and What MERV Rating Do I Need?

Once you locate your old furnace filter and figure out when it should be replaced, it’s time to choose a replacement. That means determining 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 indicates the effectiveness of air filters at trapping airborne particles. The rating scale ranges from 1 to 20, with bigger numbers indicating a greater ability to filter small particles.

Experts say a filter with a MERV rating between 8 and 13 offers an appropriate balance between having healthy indoor air quality without overly 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 properly is crucial for the efficient operation of the unit. Air filters are designed to be installed in a specific 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 toward the furnace or air conditioner, which is the direction of the airflow. If you're not sure about the airflow direction, try 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 air conditioning unit.

Many people have difficulty remembering which direction to point an air filter. To help remember, consider snapping a quick photo 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 be installed. A perfect time to inquire about this is during a routine furnace maintenance call.

How to Change a Furnace Air Filter

Switching out the filter on your furnace or air conditioner is a quick and easy process. Here is a step-by-step breakdown of how to take out a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Make sure to turn off your furnace before starting up the process.
  2. Find the furnace filter: Typically, the filter is located within 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 similarly.
  3. Remove the old filter: Be diligent not to knock out any dust or particles.
  4. Document the date: Write down the date of replacement on the new filter's frame. This will help your family keep track of when it's time for another replacement.
  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 the old filter you are replacing.
  6. Secure the filter: Make sure the new filter fits correctly and close any latches or clips that hold it in place.
  7. Turn on your furnace: Once the replacement filter is safely secured, you can turn your furnace back on.

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

The short answer is, yes, a dirty air filter can cause a furnace to quit working or limit its lifespan. Changing your furnace or air conditioning filter is one of the simplest things you can do to keep your system working correctly.