Picking out the correct 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 critical role in keeping its system working safely, efficiently and for a long time.

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

Making certain your furnace uses a clean filter that is appropriate for your needs is not only about keeping your furnace working efficiently. It’s also about delivering excellent indoor air quality for your home.

The quality of the air your family breathes is important to the heating specialists at Solar Air Inc.. We've long worked with an eye on enhancing indoor air quality in Fort Lauderdale. 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?

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. Soiled filters cause the system to worker harder than it should because it takes more energy to force air through the plugged-up filter.

Officials advise checking 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 will probably 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 normally found in the return air duct or blower compartment before the return air reaches 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 type of furnace, the filter may be positioned on the right, left, bottom or in some cases, on the inside of the furnace. It's generally housed inside of a slot, frame or cabinet for convenient access and replacement. Always refer to your furnace's owner manual for important information concerning filter location of the furnace in your home.

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 conditioning filter are effectively identical. 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 HVAC system.

They each remove dust, allergens, bacteria and other airborne debris 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 Do I Need?

Once you find your old furnace filter and figure out when it should be substituted for a clean one, it’s time to pick a replacement. That means determining the level of filtration that you need. One method to do 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 higher numbers indicating a greater ability to filter small particles.

Experts say a filter with a MERV rating between 8 and 13 offers a good balance between having adequate indoor air quality without needlessly restricting airflow. However, people with some 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 Conditioner

Putting an air filter in a furnace or air conditioner correctly is necessary 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 in the direction of the furnace or air conditioning unit, which is the direction of the airflow. If you're doubtful about the airflow direction, try to remember that air always moves from the return duct and then to the heat or cooling source. Therefore, make certain the arrow points at the furnace or air conditioning unit.

Many people are confused by which direction to point their system's air filter. To help remember, consider taking a quick picture with your mobile 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 point. A handy time to ask about this is during a routine furnace maintenance call.

How to Change a Furnace Air Filter

Changing the filter on your furnace or AC is a quick and easy process. Here is a step-by-step rundown of how to take out a dirty air filter and replace it with a new one:

  1. 1. Turn off your furnace: Make a point to shut 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 note of which direction the arrow points on the filter, because you’ll want the arrow on the replacement filter to point the same way.
  3. Take out the old filter: Be careful not to knock out any dust or particles.
  4. Note the date: Write down the date you changed filters on the new filter's frame. This will help you keep track of when it's time for another replacement.
  5. Insert 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 old filter you are replacing.
  6. Secure the filter: Make sure the new filter fits nicely and close any latches or clips that hold it in the compartment.
  7. Turn on your furnace: Once the replacement filter is safely in place, you can turn your furnace back on.

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

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