Selecting the right furnace filter and changing it when it becomes 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 clogged furnace filter loses its effectiveness, enabling potentially harmful particles to flow through your home. It also restricts 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 working efficiently. It’s also about delivering good indoor air quality for your residence.

Your health is important to the heating pros at J & J Air Conditioning. We've long focused on bettering indoor air quality in Eastland. 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?

How Often to Replace the Air Filter in a Furnace

Experts stress it's 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 extra effort to force air through the plugged-up filter.

Officials advise examining your furnace filter every 30 days and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will be gray or black from dirt or dust. People who have pets will very likely need to replace their furnace air filter more often, because an effective air filter will trap pet hair circulating in a home.

Where Is the Air Filter in My Furnace?

In general, a furnace air filter is commonly found in the return air duct or blower compartment before the return air gets to the furnace. This makes sure 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 found on the right, left, bottom or in some cases, on the inside of 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 regarding filter location of your furnace.

Is a Furnace Filter the Same as an Air Filter?

The easy answer is, yes. In HVAC, a furnace filter and an air filter or air conditioner filter are basically 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 home.

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 a MERV Rating and What MERV Rating Do I Need?

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

MERV stands for Minimum Efficiency Reporting Values. The MERV rating calculates the effectiveness of air filters at trapping airborne contaminants. The rating scale ranges from 1 to 20, with higher numbers indicating enhanced capabilities to filter small particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having good indoor air quality without unnecessarily restricting airflow. However, people with some 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 Conditioner

Putting an air filter in a furnace or air conditioner correctly is necessary for the efficient operation of the unit. 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 installed with this arrow pointing toward the furnace or air conditioner, which is the direction of the airflow. If you're not sure about the airflow direction, remember that air always moves from the return duct towards the heat or cooling source. Therefore, make sure the arrow points at the furnace or air conditioning unit.

Many people struggle with which direction to point 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 go. A great time to do this is during a scheduled furnace maintenance call.

How to Change a Furnace Air Filter

Changing the filter on your furnace or air conditioning system is a simple process. Here is a step-by-step rundown of how to remove a dirty air filter and replace it with a new one:

  1. 1. Turn off your furnace: Make a point to switch off your furnace before starting up the process.
  2. Locate the furnace filter: Typically, the filter is positioned in 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 clean filter to point in the same direction.
  3. Slide out the old filter: Be careful not to knock out any dust or debris.
  4. Record 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. 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 securely and close any latches or clips that hold it in the compartment.
  7. Turn on your furnace: Once the new filter is completely secured, you can turn your furnace back on.

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

The shortest answer is, yes, a dirty air filter can cause a furnace to stop working or limit its lifespan. Changing your furnace or air conditioner filter is one of the best things you can do to keep your system working effectively.