# Ultrasonic humidifiers--what makes the mist?

**URL:** <https://boards.straightdope.com/t/ultrasonic-humidifiers-what-makes-the-mist/156366>\
**Category:** Factual Questions\
**Created:** [February 20, 2003, 5:51pm UTC](https://boards.straightdope.com/t/ultrasonic-humidifiers-what-makes-the-mist/156366 "2003-02-20T17:51:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [February 20, 2003, 5:51pm UTC](https://boards.straightdope.com/t/ultrasonic-humidifiers-what-makes-the-mist/156366/1 "2003-02-20T17:51:24Z")

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The only thing I have been able to find about ultrasonic humidifiers is that they create a mist by passing the water over a diaphragm vibrating at an ultrasonic frequency.

OK, but why does passing water over a diaphragm vibrating at an ultrasonic frequency turn it into mist? I have a couple of these and it’s pretty cool to take the nozzle off and watch it fire up, that mist coming bubbling up the exhaust chute. But I don’t know what creates the mist, why it rises inside the humidifier, and then falls again when it leaves.

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [February 20, 2003, 6:09pm UTC](https://boards.straightdope.com/t/ultrasonic-humidifiers-what-makes-the-mist/156366/2 "2003-02-20T18:09:08Z")

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[More than you ever wanted to know.](http://home.howstuffworks.com/framed.htm?parent=humidifier.htm&url=http://www.pnl.gov/fta/14_ultrahumid/14_ultrahumid.htm)

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**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [February 20, 2003, 6:25pm UTC](https://boards.straightdope.com/t/ultrasonic-humidifiers-what-makes-the-mist/156366/3 "2003-02-20T18:25:30Z")

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> [@](#):
>
> The transducer is designed so that this compression is directed at the surface of the water where cavitation occurs, broken capillary waves are formed, and minute droplets break the surface tension of the water and quickly dissipate into the air forming a fog or mist. The droplets in the mist are typically 1 micron in diameter.

Wow. Thanks. I did check howstuffworks and did not find that page.