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 role in keeping its system operating 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 limits airflow, which can damage your furnace and shorten its life span.

Making certain your furnace uses a clean filter that is ideal for your needs is not just about keeping your furnace operating efficiently. It’s also about creating excellent indoor air quality for your residence.

The quality of the air your family breathes is important to the heating pros at Northwest Services. We've long been dedicated to bettering indoor air quality in Swanton. Here, we’ve answered common 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 is critical to replace dirty air filters in a furnace or air conditioner periodically. 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 inspecting your furnace filter every month 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 dogs and cats will very likely need to replace their furnace air filter more often, because a good 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 installed in the return air duct or blower compartment before the return air reaches the furnace. This is so air entering the system is filtered before it passes through the furnace components and is heated.

Depending on the furnace brand, the filter may be located 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 details concerning filter location of your particular brand and model of furnace.

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 AC filter are effectively identical. While they might be called different things based on the current season— hot or cold—they are all filters that clean the air in your home.

They each get rid of dust, allergens, bacteria and other contaminants 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 locate your old furnace filter and figure out 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 method to do this is by selecting an appropriate MERV rating for your needs.

MERV is an abbreviation for Minimum Efficiency Reporting Values. The MERV rating calculates the effectiveness of air filters at trapping airborne particles. 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 might need to use a filter with a higher MERV rating.

How to Place the Air Filter in a Furnace or Air Conditioning System

Installing an air filter in a furnace or air conditioner the proper way 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 placed in the unit with this arrow pointing in the direction of the furnace or AC, which is the direction of the airflow. If you're not sure about the airflow direction, it may be helpful to remember that air always moves from the return duct to the heat or cooling source. Therefore, make certain the arrow points at the furnace or air conditioner.

Many people struggle with which direction to install their system's 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.

Changing Your Furnace's Air Filter

Replacing the filter on your furnace or AC is a simple 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. Turn off your furnace: Make sure to turn off your furnace before starting up the process.
  2. Locate the furnace filter: Typically, the filter is located inside 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 in the same direction.
  3. Take out the old filter: Be diligent not to knock out any dust or dirt.
  4. Note the date: Write down the date you replaced the filter on the new filter's frame. This will make it easier to keep track of when it's time for the next change.
  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 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 place.
  7. Turn on your furnace: Once the replacement filter is completely in place, you can turn your furnace back on.

Can a Dirty Air Filter Cause Problems for a Furnace?

The shortest answer is, yes, a dirty air filter can cause a furnace to cease working or shorten its lifespan. Changing your furnace or air conditioning filter is one of the simplest things you can do to keep your system operating effectively.