Air purifiers in classrooms are more and more common due to the pandemic to reduce virus spread. Unfortunately, most classrooms do not get the full benefit of air purifiers because most of the time teachers end up turning them off or down!
Why Are Teachers Turning Air Purifiers Off?
In November 2021, GPS commissioned a National Teachers Survey of 750 US teachers with air purifiers in their classes. The results are astounding:
- Nearly 70% of teachers turn off, or down, the HEPA filter due to noise.
- 40% of teachers agree that noise from the HEPA filters makes it harder to teach/harder to learn.
- 31% of teachers indicate that students ask for the in-room air filter to be turned off or down either daily (11%) or weekly (20%).
- 67% of teachers indicate they most often have the HEPA filter set to a level below High (including off). Most purifiers are spec’d to run on maximum setting.
The Need For Effective, Low-Disturbance Classroom Air Purifiers
We launched Smart Air with a DIY air purifier, designed to provide low-cost, affordable clean air at a time when companies were charging thousands for air purifiers.
Later when we built the original Blast and Blast Mini air purifiers, our priority was building:
- The most effective air purifier (highest CADR) at the lowest cost.
- A purifier that was quiet even on high.
After the Blast and Blast Mini MkII were released, it was clear how important the second priority was to our users.

The Blast Difference

It’s hard to overstate how critical noise is to the decision-making process. Few manufacturers prioritize low noise on the top setting, yet the marketing will focus on how great the performance is at the highest levels.
But it’s not just schools. Even in hospitals with signs such as “Do not turn down, this machine is providing you with clean air”, purifiers are turned down or off.
What Level of Noise is Acceptable in Most Workplaces?
The maximum decibels you should aim for is 50 dBA but ideally 40 dBA in a classroom. While this difference may not seem much, an increase of 10 dB means the purifier is “about” twice as loud for human ears or 10 times the power in electronic terms. In other words, an air purifier marked as 50 dB is double the loudness of a 40 dB air purifier!
How to Work Out the Best Purifier for Your Space
Want to know how to calculate what CADR an air purifier needs to clean your space?
Read More: How to Calculate What CADR Air Purifier I Need
Or check out our guide on how to choose the best air purifier.
What We Do
Founded by University of Chicago Professor Thomas Talhelm, Smart Air created a $30 air purifier in 2013 that changed the industry. It’s not just an air purifier.
It’s a message that the clean air industry needs fixing, and we’re doing that.
Check out our line of incredibly effective air purifiers at an honest price.

Honest air purifiers
No gimmicks. Fair price. Extremely effective.
Free Guide to Breathing Safe
Want to learn more about Air Pollution? Join thousands more and stay up to date on protecting your health.