What Does an Air Filter Do in Your House?

What do air filters do, and how does an air filter work? The idea seems pretty simple, but purifying the air can be a somewhat complex task considering there are 60+ sources of indoor air pollution. Not to mention the hundreds of products that can release volatile organic compounds (VOCs) into the air.

An air filter clearly serves a purpose, but does every home need one? The short answer is yes! But, read on because this guide will give you more information about what air filters are, why they are used, and why every home with an HVAC system can benefit from having them.

What is an Air Filter?

Let’s start with the basics by defining what an air filter is. An air filter is essentially a screen that fits into a compartment of the HVAC system to clean the air as it circulates through a home.

Air filters are an aftermarket product with a longevity that typically spans 1-6 months for disposable filters. Washable air filters can last up to five years.

The Purpose of an Air Filter

What does an air filter do in your house once it’s installed? The primary air filter purpose is cleaning the air inside so it’s healthier to breathe. You may not realize that many homes have air quality that is worse than outside, and your home could be one of them. If you don’t have proper ventilation and air filters for purification contaminants can build up inside.

Air filters are also a part of the overall HVAC system. They serve as a first line of defense that protect HVAC components from contaminants.

What air filters are made of can influence whether they have a specialized purpose. For example, air filters with carbon are particularly good at removing odors from the air.

How Do Air Filters Work?

Understanding how air filters work can help you decide which filter is best for a specific purpose. All air filters work in a similar fashion:

  • Air passes through the filter screen.
  • As the air passes through, the filter media (material) catches particulate matter such as pollen, dust, pet dander, dirt and allergens. Some types of air filters can even remove bacteria and viruses from the air.
  • Every second as air passes through the filter media contaminants build up. Eventually, the filter gets too clogged and airflow is reduced.
  • Eventually, the filter gets too clogged and airflow is reduced.
  • The air filter is then replaced, and the process continues.
Where air filters differ most is the media that is used. Filter media quality and quantity influences the size of air particles that can be captured, how they are captured and airflow through the system.

MERV Ratings - Better Purification, Restricted Airflow

People put a lot of emphasis on the Minimum Efficiency Reporting Value (MERV). The MERV rating is important beyond indicating how well the filter purifies the air. It can also affect airflow, which has a negative impact on the HVAC equipment, energy efficiency and your comfort.

MERV ratings range from 1 (least efficient) to 20 (most efficient). Air filters with a MERV rating of 14 or higher capture more particulates but they also restrict the airflow more and get clogged faster.

Read More: All About MERV Ratings

Are Air Filters Necessary?

If a primary air filter function is to clean the air, is it necessary to use one in a home with good air quality? Do air filters make a difference if the air is healthy? Do allergen furnace filters work well enough to eliminate the use of an air purifier?

The short answer is yes, because air filters don’t just clean the air effectively. They also protect your HVAC equipment.

an HVAC system outside the house

Air Filters Keep Debris Out of the HVAC Equipment

Air filters keep debris and air particles out of sensitive components. Two places where dust and dirt could accumulate are the duct system and air handler. The debris will build up over time creating a variety of issues, along with polluting the air inside.

Air Filters Improve Efficiency and Reduce Equipment Wear

Do you like wasting energy and paying more than you need to heat and cool your home? If the answer is no, then you’ll want to replace your air filters regularly.

With less dirt and debris in the system, HVAC equipment runs more efficiently. The opposite is true if you have no air filter or the air filter is so dirty it’s restricting airflow. When that happens parts like the fan motor will have to work harder, which means more electricity is consumed. The fan motor is also more likely to need repair.

Even if you’re lucky enough to have great air quality inside without an air filter, your HVAC equipment still needs that layer of protection to work efficiently.

Find the best air filters for your home - search by MERV rating, media type or size


Frequently Asked Questions

How does an HVAC air filter work? 

An HVAC air filter works by capturing and removing various airborne particles and contaminants from the air circulating through your heating, ventilation, and air conditioning (HVAC) system. The filter traps dust, pollen, pet dander, mold spores, and other pollutants, preventing them from recirculating into your living spaces. 

Why is it important to have a functioning HVAC air filter? 

Having a functioning HVAC air filter is crucial for maintaining indoor air quality. It helps to remove allergens, pollutants, and particles from the air, which can enhance respiratory health and reduce allergic reactions. Additionally, a clean filter ensures that the HVAC system operates efficiently, preventing it from becoming clogged and potentially damaging the system. 

How often should I change my HVAC air filter? 

The frequency of changing your HVAC air filter depends on various factors, including the type of filter, the level of pollutants in your environment, and the manufacturer's recommendations. As a general guideline, it is advisable to check your filter at least once a month and replace it when it appears dirty or clogged. Some filters may need replacement every three months, while others, such as high-efficiency filters, may last up to six months. 

How can a dirty air filter impact my HVAC system? 

A dirty air filter can hinder the airflow in your HVAC system, causing it to work harder to circulate air. This extra strain can lead to reduced energy efficiency, higher utility bills, and potentially even damage to the system. Additionally, a clogged filter can allow dust and debris to accumulate on the system's components, decreasing its lifespan and requiring more frequent maintenance. 

Are there different types of HVAC air filters available? 

Yes, there are different types of HVAC air filters available on the market. The most common types include fiberglass filters, pleated filters, electrostatic filters, and high-efficiency particulate air (HEPA) filters. Each type has its own filtration capabilities, lifespan, and price range. It's essential to choose a filter that suits your specific needs and consult the manufacturer's guidelines for your HVAC system. 

Does a higher MERV rating indicate better filtration? 

The Minimum Efficiency Reporting Value (MERV) rating is a scale that measures the effectiveness of an air filter. While a higher MERV rating typically indicates better filtration and the ability to capture smaller particles, it may not always be necessary for residential HVAC systems. Higher MERV-rated filters may also restrict airflow, which can strain the system. It is advisable to consult the HVAC manufacturer's recommendations or seek professional advice when choosing the appropriate MERV rating for your specific system.