Choosing the right 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 vital function in keeping its system running safely, efficiently and for a long time.

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

Making certain 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 providing excellent indoor air quality for your household.

The health of your family is important to the heating professionals at JTech Mechanical. We've long worked with an eye on improving indoor air quality in Magnolia. 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 periodically. Dirt-clogged filters cause the system to worker harder than it should because it takes extra effort to force air through the plugged-up filter.

Officials suggest examining your furnace filter every month and replacing it if it’s dirty. You’ll know if it is dirty because it will coated with dirt or dust. People who have pets that shed will probably want 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 usually found in the return air duct or blower compartment before the return air gets to 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 model, the filter may be found on the right, left, bottom or in some cases, within the furnace. It's usually housed in a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for facts 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 essentially identical. While people may call them different things based on the current season— warm or chilly months—they are all filters that clean the air in your residence.

They each get rid of dust, allergens, bacteria and other particulates from the air that is drawn into the furnace and air conditioning system, making certain the air circulating throughout your home is clean and safe.

What Are MERV Ratings and What MERV Rating Do I Need?

Once you locate your old furnace filter and determine when it should be replaced, 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 selecting an appropriate MERV rating for your needs.

MERV is an abbreviation for Minimum Efficiency Reporting Values. The MERV rating measures the effectiveness of air filters at trapping airborne molecules. The rating scale ranges from 1 to 20, with greater numbers indicating enhanced capabilities to filter tinier particles.

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

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

Installing an air filter in a furnace or air conditioner the proper way is important for the efficient operation of the heating or cooling system. Air filters have a particular 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 toward the furnace or air conditioning unit, 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, be sure that the arrow points in the direction of the furnace or air conditioning unit.

Many people struggle with which direction to face an air filter. To help remember, consider taking a quick picture with your mobile phone after the filter has been properly 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 do this is during a routine furnace maintenance call.

Changing Your Furnace's Air Filter

Changing the filter on your furnace or air conditioning system 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. Turn off your furnace: Make sure to switch off your furnace before beginning the process.
  2. Locate the furnace filter: Typically, the filter is positioned 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 clean filter to point similarly.
  3. Take out the old filter: Be careful not to knock out any dust or debris.
  4. Note the date: Write down the date of replacement on the new filter's frame. This will help your family keep track of when it's time for you to change it again.
  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 secure it in the compartment.
  7. Turn on your furnace: Once the replacement filter is completely in place, you can turn your furnace back on.

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

The short answer is, yes, a dirty air filter can cause a furnace to stop 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 efficiently.