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

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

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

Your health is important to the HVAC specialists at Service Max Heating & Air Conditioning. We've long worked with an eye on bettering indoor air quality in Arlington. 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?

Experts stress it's critical to replace dirty air filters in a furnace or air conditioner regularly. Dirty filters cause the system to worker harder than it should because it takes more energy to pull air through the plugged-up filter.

Officials suggest inspecting your furnace filter monthly and replacing it if it’s dirty. You’ll know if it is dirty because it will filled with dirt or dust. Homeowners who have pets that shed will probably want to replace their furnace air filter more often, because an effective air filter will trap pet hair circulating in a home.

Locating Your Furnace's Air Filter

In general, a furnace air filter is usually installed 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 moves through the furnace components and is heated.

Depending on the type of furnace, the filter may be located on the right, left, bottom or in some cases, on the inside of the furnace. It's generally housed in a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for information regarding filter location of your particular brand and model of furnace.

Are Air Filters and Furnace Filters the Same Thing?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are essentially the same thing. 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 remove dust, allergens, bacteria and other contaminants from the air that is drawn into the furnace and air conditioning system, ensuring the air distributed throughout your home is clean and safe.

What Is a MERV Rating and What MERV Rating Should I Have?

Once you find your old furnace filter and figure out when it should be substituted for a clean one, it’s time to choose a replacement. That means deciding on the level of filtration that you need. One method to do this is by choosing 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 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 appropriate balance between having adequate indoor air quality without unnecessarily restricting airflow. However, people with specific health conditions may need to use a filter with a higher MERV rating.

Which Way to Put the Air Filter in a Furnace or AC Unit

Installing an air filter in a furnace or air conditioner the proper way is crucial for the efficient operation of the unit. Air filters are supposed to face a certain direction, indicated by an arrow printed on the side of the filter frame. The filter should be put in with this arrow pointing toward the furnace or AC, which is the direction of the airflow. If you're unsure about the airflow direction, try to remember that air always moves from the return duct towards the heat or cooling source. Therefore, make sure the arrow points in the direction of the furnace or air conditioner.

Many people have difficulty remembering 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 point. A great time to inquire about this is during a regular furnace maintenance appointment.

How to Replace Your Furnace Air Filter

Replacing the filter on your furnace or air conditioner is an easy process. Here is a step-by-step list of how to retreive a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Be sure to turn off your furnace before beginning the process.
  2. Find the furnace filter: Typically, the filter is located in 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 replacement filter to point in the same direction.
  3. Take out the old filter: Be mindful not to knock out any dust or debris.
  4. Document 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 the next change.
  5. Slide in 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 correctly and close any latches or clips that secure it in the unit.
  7. Turn on your furnace: Once the new filter is properly secured, you can turn your furnace back on.

Will a Dirty Air Filter Cause Problems for a Furnace?

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