What Air Exchange Rate is & And Why It Matters


Are you getting enough fresh air?

We often don't think about it, but every day millions of cubic feet of outdoor air cycle through our homes and offices. And while air flow might sound boring to some, it’s important to think about because it brings in gases like oxygen, nitrogen and others.

Especially when you realize we spend over 90% of our time indoors.

And so, today we’re looking at the process of air exchange rate which plays a vital role in creating healthy indoor air quality. We’re also share some tips for how to improve your own indoor air quality during cold winter months.

What is Air Exchange Rate?

Air Exchange Rate (AER) is a scientific concept that refers to the way in which air moves in and out of an enclosed space. AER is also sometimes referred to as Air Changes Per Hour (ACH) because it’s measured by the number of times the air is replaced in a room.

Depending on the purpose of the space, the requirements will also change. For example, bedrooms will have a lower expected number of air exchanges than a kitchen or laundry room. Medical facilities, like hospitals, also require much higher air exchange rates to protect vulnerable populations.

How to Calculate Air Exchange Rate

Whether you are a curious community scientist, an enthusiastic researcher, or someone who cares about clean air and healthy living—learning how to calculate the air exchange rate is essential for understanding the movement of air through buildings.

Here’s how to measure air exchange rates in 3 steps:

  1. Measure the total airflow volume of a room in Cubic Feet per Minute (CFM). You can do this with a tool like an anemometer.
  2. Multiple the total CFM by 60 minutes in an hour.
  3. Divide that number by the volume of the room in cubic feet.

 AER = Room’s Cubic Feet per Minute x 60 minutes ÷ Room Volume in Cubic feet

Why Air Exchange Rate Matters

Every day, we are exposed to an ever-growing number of pollutants, bacteria, and particulate matter in our environment. And that’s not just bad for your health – it’s also bad for productivity. Employees are less productive when exposed to poor indoor air quality. High levels of particulate matter (PM) affect your brain, reducing response time and lowering you focus.

So, it's more important now than ever before to protect our indoor and outdoor air quality. Whether you’re at home, school, or the office.

Having a healthy AER is also especially important for people with respiratory illnesses, allergies, and other health concerns. Since it determines issues like indoor air quality, ventilation, and pollutant removal, you need to ensure the airflow complies with local regulations.

How to Improve Indoor Air Quality

If you want to improve your indoor air quality and air exchange rate, here are a few steps you can take:

  • Install a ventilation system: To replace stale air with fresher air.
  • Adding an air cleaner: This will reduce airborne allergens and pollutants.
  • Purchase an air quality monitor: So you can see your air quality levels in real time.

Improving air quality in our homes isn't just about making ourselves feel better, it's about taking steps to protect our loved ones as well. By following the tips, you can make a difference. One way we can help fight this global problem is by monitoring our own local air quality, then we can make informed decisions and take steps to improve our environment.

Worried about air quality? 

Monitor the Particulate Matter levels around the world with our free, real-time PurpleAir Map or join PurpleAir's mission to make air quality data accessible to everyone by investing in an air quality monitor for your home.

Together, we can be informed and make changes in our daily habits and the community to improve air quality.