Picking out the ideal 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 part in keeping its system operating safely, efficiently and for a long time.

A dirty furnace filter loses its effectiveness, permitting potentially harmful particles to move through your home. It also slows 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 creating healthy indoor air quality for your home.

The health of your family is important to the heating and cooling professionals at Comfort Zone, LLC. We've long focused on enhancing indoor air quality in Cape Coral. 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 vital to replace dirty air filters in a furnace or air conditioner periodically. Dirty filters cause the system to worker harder than it should because it takes more energy to pull air through the plugged-up filter.

Officials suggest checking your furnace filter monthly and replacing it if it’s dirty. You’ll know if your filter needs changing because it will be gray or black from dirt or dust. Homeowners who have pets that shed will probably want to replace their furnace air filter more often, because an effective 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 gets to the furnace. This ensures air flowing into the system is filtered before it goes through the furnace components and is heated.

Depending on the type of furnace, the filter may be located on the right, left, bottom or in some cases, on the inside of the furnace. It's typically housed within a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for details about 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 AC filter are basically the same. While they might be called different things 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 airborne debris 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 a MERV Rating 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 picking the level of filtration that you need. One approach to this is by choosing an appropriate MERV rating for your needs.

MERV is short 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 tinier particles.

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

Which Way to Put the Air Filter in a Furnace or AC Unit

Putting an air filter in a furnace or air conditioner properly is important 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 installed with this arrow pointing toward the furnace or AC, which is the direction of the airflow. If you're not sure about the airflow direction, 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 AC.

Many people are confused by which direction to install their system's air filter. To help remember, consider taking a quick picture with your cell 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 ask about this is during a scheduled furnace maintenance appointment.

How to Replace Your Furnace Air Filter

Changing the filter on your furnace or AC is an easy process. Here is a step-by-step breakdown of how to retreive 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. Find the furnace filter: Typically, the filter is found 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 new filter to point in the same direction.
  3. Slide out 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 make it easier to keep track of when it's time for another replacement.
  5. Slide in new filter: Put in the new filter with the arrow pointing at 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 nicely and close any latches or clips that lock it in the compartment.
  7. Turn on your furnace: Once the clean filter is safely in place, 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 cease working or decrease its lifespan. Changing your furnace or AC filter is one of the easiest things you can do to keep your system operating correctly.