Picking out the correct 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 crucial part in keeping its system working safely, efficiently and for a long time.

A clogged furnace filter loses its effectiveness, permitting potentially harmful particles to circulate 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 good indoor air quality for your residence.

Your health is important to the heating and cooling pros at LTS Plumbing & Heating Inc.. We've long focused on improving indoor air quality in Shamokin and Sunbury. 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 vital 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 extra effort to force air through the plugged-up filter.

Officials advise examining your furnace filter every month and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will filled with dirt or dust. Those who have pets will very likely want to replace their furnace air filter more often, because a quality air filter will trap pet hair circulating in a home.

Locating Your Furnace's Air Filter

In general, a furnace air filter is commonly located in the return air duct or blower compartment before the return air goes back into the furnace. This ensures air flowing into the system is filtered before it moves through the furnace components and is heated.

Depending on the furnace brand, the filter may be positioned on the right, left, bottom or in some cases, inside the furnace. It's typically housed within a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for facts about filter location of the furnace in your home.

Are Air Filters and Furnace Filters the Same Thing?

The simple answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are basically the same. While people might refer to them differently based on the current season— hot or cold—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, ensuring the air distributed throughout your home is clean and safe.

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

Once you track down your old furnace filter and determine when it should be replaced, it’s time to pick a replacement. That means picking 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 indicates the effectiveness of air filters at trapping airborne particles. The rating scale ranges from 1 to 20, with bigger numbers indicating enhanced capabilities to filter small particles.

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

Where to Insert the Air Filter in a Furnace or Air Conditioning System

Putting an air filter in a furnace or air conditioner the proper way 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 in the direction of the furnace or AC, which is the direction of the airflow. If you're unsure 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 in the direction of the furnace or air conditioner.

Many people have difficulty remembering which direction to face their air filter. To help remember, consider taking a quick picture with your cell 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 great time to do this is during a routine furnace maintenance call.

How to Change a 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 take out a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Make sure to shut off your furnace before starting the process.
  2. Look for 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 the same way.
  3. Take out the old filter: Be diligent not to knock out any dust or particles.
  4. Document the date: Write down the date of replacement on the new filter's frame. This will make it easier to keep track of when it's time for another replacement.
  5. Put 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 your last filter.
  6. Secure the filter: Make sure the new filter fits securely and close any latches or clips that secure it in place.
  7. Turn on your furnace: Once the replacement filter is completely installed, you can turn your furnace back on.

Can a Dirty Air Filter Cause Problems for a Furnace?

The simple answer is, yes, a dirty air filter can cause a furnace to cease working or limit its lifespan. Changing your furnace or air conditioner filter is one of the easiest things you can do to keep your system operating correctly.