Picking out the correct 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 critical role in keeping its system running safely, efficiently and for a long time.

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

Ensuring your furnace uses a clean filter that is ideal for your needs is not merely about keeping your furnace running efficiently. It’s also about creating excellent indoor air quality for your home.

Your health is important to the HVAC specialists at County Line Mechanical LLC. We've long focused on bettering indoor air quality in Reinholds. Here, we’ve answered frequent questions about HVAC filters, including that especially 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

It is critical to replace dirty air filters in a furnace or air conditioner routinely. Soiled filters cause the system to worker harder than it should because it takes extra effort to move air through the plugged-up filter.

Officials recommend examining your furnace filter every 30 days and replacing it if it’s dirty. You’ll know if your filter needs changing because it will coated with dirt or dust. Homeowners who have pets will likely want to replace their furnace air filter more often, because a quality 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 usually located in the return air duct or blower compartment before the return air goes back into the furnace. This is so air entering the system is filtered before it moves through the furnace components and is heated.

Depending on the type of furnace, the filter may be positioned 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 details about filter location of the furnace in your home.

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 air conditioner filter are basically identical. While people might refer to them differently based on the current season— warm or chilly months—they are all filters that clean the air in your home.

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 figure out when it should be changed, it’s time to select a replacement. That means picking the level of filtration that you need. One way to do that is by choosing 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 molecules. 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 appropriate balance between having healthy indoor air quality without overly restricting airflow. However, people with certain health conditions may need to purchase a filters with a higher MERV rating.

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

Positioning an air filter in a furnace or air conditioner properly is crucial for the efficient operation of the unit. Air filters have 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 air conditioning unit, which is the direction of the airflow. If you're doubtful about the airflow direction, try to remember that air always moves from the return duct and then to the heat or cooling source. Therefore, make certain the arrow points in the direction of the furnace or AC.

Many people are confused by which direction to face their air filter. To help remember, consider taking a 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 inquire about this is during a scheduled furnace maintenance appointment.

How to Replace Your Furnace Air Filter

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

  1. Turn off your furnace: Make sure to turn off your furnace before beginning the process.
  2. Look for the furnace filter: Typically, the filter is positioned within 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 the same way.
  3. Remove the old filter: Be mindful 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 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 old filter you are replacing.
  6. Secure the filter: Make sure the new filter fits nicely and close any latches or clips that hold it in the unit.
  7. Turn on your furnace: Once the clean filter is completely installed, you can turn your furnace back on.

Can a Dirty Air Filter Damage My Furnace?

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