Choosing the correct 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 critical role in keeping its system operating safely, efficiently and for a long time.

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

Ensuring your furnace uses a clean filter that is ideal for your needs is not merely about keeping your furnace operating efficiently. It’s also about creating healthy indoor air quality for your home.

Your health is important to the heating pros at Struven Heating & Cooling. We've long been dedicated to bettering indoor air quality in Crown Point. 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 Should I Replace My Furnace Air Filter?

It is important to replace dirty air filters in a furnace or air conditioner routinely. Dirty 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 inspecting 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. Those who have pets will probably want 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 usually found in the return air duct or blower compartment before the return air goes back into the furnace. This makes sure 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 found on the right, left, bottom or in some cases, on the inside of the furnace. It's usually housed inside of a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for important information about filter location of the furnace in your home.

Are Air Filters and Furnace Filters the Same Thing?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or AC filter are effectively the same thing. 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 HVAC system.

They each remove dust, allergens, bacteria and other particulates from the air that is drawn into the furnace and air conditioning system, ensuring the air flowing through your home is clean and safe.

What Is a MERV Rating and What MERV Rating Do I Need?

Once you locate your old furnace filter and determine when it should be substituted for a clean one, it’s time to pick 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 is short for Minimum Efficiency Reporting Values. The MERV rating calculates the effectiveness of air filters at trapping airborne molecules. The rating scale ranges from 1 to 20, with greater numbers indicating the power to filter tinier particles.

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

Which Way to Put the Air Filter in a Furnace or Air Conditioning System

Putting an air filter in a furnace or air conditioner correctly is crucial for the efficient operation of the system. Air filters are designed to be installed in a certain direction, indicated by an arrow written on the side of the filter frame. The filter should be put in with this arrow pointing at the furnace or AC, 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 and then 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 struggle with which direction to install their air filter. To help remember, consider snapping a quick photo 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 go. A great time to inquire about this is during a scheduled furnace maintenance visit.

How to Replace Your Furnace Air Filter

Switching out the filter on your furnace or AC is a simple process. Here is a step-by-step list of how to remove a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Make sure to switch off your furnace before beginning the process.
  2. Find the furnace filter: Typically, the filter is found inside the furnace or in the air return vent. Take note of which direction the arrow points on the filter, because you’ll want the arrow on the clean filter to point similarly.
  3. Take out the old filter: Be diligent not to knock out any dust or debris.
  4. Note the date: Write down the date you replaced the filter on the new filter's frame. This will help your family 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 dirty filter you just removed.
  6. Secure the filter: Make sure the new filter fits correctly and close any latches or clips that secure it in the compartment.
  7. Turn on your furnace: Once the new filter is properly 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 stop working or reduce its lifespan. Changing your furnace or air conditioning filter is one of the best things you can do to keep your system operating efficiently.