Not sure what kind of humidifier you are looking at but here's my experience: We have 4 humidifiers. All are ultrasonic supplied with DI water. They work well but... UT humidifiers will create a foggy white residue that will stick to things in closer proximity. I don't know what it's comprised of but even DI water creates this residue. Universal Instruments was awesome in helping us with this and they even analized the residue at their lab to quickly pin-point it. If the units are close to SMT equipment (say 20 ft or less) the machines will pull this foggy residue inside and it will adhere to charged electronics. As a result, you will blow things like power supplies. Additionally, the ultrasonic pucks WILL fail in time and you will need to replace them. It is the nature of the beast and it's a bit costly. Looking back, I think we would have researched something other than ultrasonic.
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