air filter go in furnace

Although it may appear to be a simple task, ensuring that the air filter is installed in the right furnace filter direction is crucial for keeping the airflow effective and improving the air quality inside. As HVAC professionals, we’ve witnessed firsthand how improper installation can drastically reduce a system’s performance.

In this article, we’ll help you understand the direction of your furnace filter that will ensure proper air flows into your home.

Locating Your Air Filters

If you want your HVAC system to work well, the first important thing you need to do is find where the air filters are. Depending on the manufacturer and model of your HVAC system, the location of the air filter can differ greatly. You may usually find them in these places:

Blower Compartment:

The air filter is often housed in or close to the blower compartment in older and even some modern systems. The blower fan, which distributes air throughout your house, is located in this crucial component of the system. To gain access to this area, you typically have to open a panel on the furnace’s front.

Return Air Duct or Grille:

A lot of newer houses have their filters mounted on the grille or in the air return duct. With this configuration, the air is filtered as soon as it enters the HVAC system. Changing or checking these filters is usually a breeze because they are conveniently located.

Here are some other things to keep in mind when you’re trying to find your air filters

Consult Your Furnace Manual

The location of the filter and how to install it are both covered in full in your system’s manual. If you are working with a unique configuration or a less usual system layout, this information will be essential.

Visual Inspection

If you’re still confused, a quick visual check of your system should do the trick. Look out for any big metal panels or ductwork that could hide the filter. These are usually fastened with simple tools and can be easily uninstalled.

Maintenance Records

Look for notes about the placement of the filter in any maintenance documents that may have been left by specialists who installed or repaired your system. You can learn more about your system’s inner workings from these records.

Ask a Professional

Seek the advice of a trained HVAC specialist, such as one from Comfort Union, if you have questions. If you want to be ready for future maintenance, they can show you how to access and adjust your filter and give you some advice.

Which Way Should the Air Filter Arrow Point in a Furnace?

If you want to keep your furnace running efficiently and your indoor air quality high, you need to know which direction you need to put the air filter in the filter air box. To make sure your furnace works properly and the furnace air flow is maintained, the air filter’s direction is crucial, not a minor consideration.

An arrow will be printed on the side of the filter frame to help you install the air filter in your furnace. Importantly, this arrow indicates the direction in which air moves through your system. Hence, keep the return air ducts at a safe distance and direct this arrow straight at the furnace at all times.

What this means is that the air is drawn into the furnace and then flows through the furnace filters in the arrowhead direction. This allows the filter to effectively trap any airborne particles before the air is heated and distributed throughout your home.

Why Proper Airflow Direction Matters in Furnace Systems

1. Better Indoor Air Quality

One side of an air filter is usually more porous than the other due to design considerations. The filter’s function relies on this intentional design. To prevent allergens like pollen, dust, and pet dander from entering the furnace, the more porous side should be directed towards the incoming air, which is the air coming back from your house. Good indoor air quality is crucial for homes with people who suffer from allergies or have respiratory issues, so understanding the direction is very vital to preserve that.

2. Reduced Energy Consumption

In addition, the manufacturer-designed airflow path through the air furnace filters is minimized when airflow is directed correctly. Installing a filter backward causes the less porous side to be exposed to the entering air, which can significantly increase the resistance to airflow.

The furnace has to work harder to push air through the filter because of this resistance, which means more energy consumption and higher electricity costs. This additional stress can eventually wear down the blower motor and other parts of the furnace, which could cause them to break down early and cost a pretty penny to fix.

3. Enhanced Heating Efficiency

In addition, the furnace’s efficiency is improved when the airflow is directed correctly. The air that enters the furnace is as clean as it can be because the filter is able to catch impurities to its fullest capacity when the air flows through it appropriately. The effectiveness of the heat exchange mechanism depends on this cleanliness since cleaner air transmits heat more efficiently.

The accumulation of debris within the furnace, caused by either dirty air or blocked airflow, insulates the heat exchanger and diminishes its efficiency. This reduces your furnace’s heating efficiency and may cause it to overheat, which is dangerous.

4. Extended Filter Lifespan

Finally, to make sure your furnace’s air filter lasts as long as possible, you should check the direction of airflow through it. Filters can last their whole intended lifespan with proper installation, reducing maintenance expenses and the need for replacements. On the flip side, if the installation isn’t done correctly, the filter will clog up more often, which means you’ll have to replace it more often and shell out more money for maintenance.

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Consequences of Incorrect Air Filter Installation

There are a number of problems that can arise if you install your air filter backward:

  • Reduced Air Quality: Backward filters are less effective at capturing pollutants, which results in a decline in the quality of the air inside the home and may have adverse effects on health.

  • Increased HVAC Strain: Backward filters add resistance, which makes your furnace work harder. This might cause it to wear out faster and use more energy.

  • Decreased Comfort: Uneven heating or cooling, reduced ventilation, and decreased comfort levels are all possible outcomes of improper installation.

Furnace Filter Tips for Correct Installation

  • Check Arrow Direction: To ensure proper installation, make sure the new filter’s arrow points in the same direction as the previous one. For easy reference in the future, mark the direction on your furnace with a permanent marker.
  • Filter Types and Directions:
    Differentiated by the minimum efficiency reporting value (MERV) of a filter, the following are the most common types:-
    • Disposable Filters: Find the airflow arrows on the frame of the disposable filter. These need to be oriented in the direction of the airflow.
    • Reusable Filters: Usually, reusable filters do not have any designated directions for airflow. Proceed with the installation in the same manner as the prior filter.
    • HEPA Filters: To ensure the proper operation of a high-efficiency particulate air (HEPA) filter, it is important to refer to the manufacturer’s instructions.
  • Check Filter Regularly: You can tell when a filter needs to be changed by looking at it. If you live in a very dusty area or have pets, check the filter often for signs of dirt and debris buildup and replace it as soon as the manufacturer suggests or sooner if necessary to ensure cost and filtration efficiency.
  • Get an Electronic air filter monitor: If you want to ensure that your air filter is in good working condition, you need to have a filter monitoring system. It’ll let you know when it needs to be changed with replacement filters.


For optimal performance and extended life of your heating and cooling system, it is crucial to install the HVAC furnace filter properly. An increase in system performance and ideal indoor air quality are both within your reach if you adhere to the above-mentioned precise instructions for furnace filter direction. You can maintain clean air in your house and keep your system in good working order by checking and changing your filters on a regular basis.

Proper airflow and the system’s energy efficiency depend on your paying attention to the advise to position the HVAC filter and its arrow correctly. Comfort Union is the place to go for professional HVAC solutions, expert advice, and customized service. Keeping your home cozy and energy efficient is our top priority.

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