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

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

Making sure your furnace uses a clean filter that is suitable for your needs is not just about keeping your furnace operating efficiently. It’s also about providing healthy indoor air quality for your home.

The quality of the air your family breathes is important to the heating and cooling professionals at Lanz Furnace and Fireplace. We've long been dedicated to improving indoor air quality in Monroe. 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?

When Should I Replace My Furnace Air Filter?

It is 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 more energy to move air through the plugged-up filter.

Officials advise examining your furnace filter monthly and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will filled with dirt or dust. Those who have pets will likely need 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 normally found in the return air duct or blower compartment before the return air goes back into the furnace. This is so 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 positioned on the right, left, bottom or in some cases, on the inside of the furnace. It's typically housed in a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for facts 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 conditioner 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 residence.

They each remove dust, allergens, bacteria and other airborne debris from the air that is drawn into the furnace and air conditioning system, ensuring the air circulating throughout your home is clean and safe.

What Is the MERV Rating System and What MERV Rating Do I Need?

Once you find your old furnace filter and determine when it should be substituted for a clean one, it’s time to select a replacement. That means deciding on the level of filtration that you need. One way to do that is by choosing an appropriate MERV rating for your needs.

MERV is short 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 the power to filter small particles.

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

Which Way to Put the Air Filter in a Furnace or Air Conditioner

Positioning an air filter in a furnace or air conditioner correctly is necessary for the efficient operation of the heating or cooling system. Air filters are supposed to face a particular 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 at the furnace or AC, which is the direction of the airflow. If you're doubtful about the airflow direction, 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 conditioner.

Many people are confused by which direction to install their 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 appointment.

How to Change a Furnace Air Filter

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

  1. Turn off your furnace: Make sure to shut off your furnace before starting the process.
  2. Locate the furnace filter: Typically, the filter is located 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 new filter to point the same way.
  3. Take out the old filter: Be mindful not to knock out any dust or debris.
  4. Record the date: Write down the date of replacement 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 your last filter.
  6. Secure the filter: Make sure the new filter fits correctly and close any latches or clips that secure it in the unit.
  7. Turn on your furnace: Once the new filter is properly installed, you can turn your furnace back on.

Can a Dirty Air Filter Cause Problems for a Furnace?

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