The wife & I have been using 3 different humidifiers to try to get a comfortable sleeping environment for us and baby Alexis. I would like to take a moment to report my findings as they may prove to be both surprising and beneficial to other users of humidifiers.

Main points:
1. Not all humidifiers work the same way.
2. Some humidifiers are really bad.

If you do a search for humidifiers on amazon you find hundreds of them with varying humidifying methods.
Here I will list the types in order of worst to best:

Ultrasonic or “Cool Mist”– Cheap and easy to manufacture, these produce cool mist by means of ultrasonic sound vibrations.  These are by far the most frequently seen type of humidifiers I’ve seen while browsing for them. They are also the absolute worst for health.  The EPA has listed these as the single most dangerous humidifier in existence. They not only spread any and all microbes in the water (mildew & other bacteria) into the air, but they also contaminate your breathing air with the minerals found in water. Here’s the deal folks.. These minerals do not belong in your lungs, throat & sinuses. Put a pot of water on the stove and boil it off, see the left over residue? Ultrasonic humidifiers send that stuff into the air for you to breath in. If your city puts chlorine or fluoride in your water, guess what – you’re breathing it in. If you have well water this is especially horrific as it produces a bitter metallic odor and after 3 days of use will have your nasal passages wreaking in pain. If you continue to use these long term you will begin to notice a fine white powder all over EVERYTHING in the area. If you insist on using of these humidifiers use nothing but store purchased distilled water in them to prevent chemical contamination of your breathing air, but nothing will help you against the spread of germs.

Evaporation – These humidifiers transmit moisture into the air by using a fan to blow air through a moistened absorbent material, usually a spongy filter.  This is also a good way to produce massive amounts of any kind of microbe that thrives in moist conditions. Think of a continuously wet gym sock left to mildew for weeks, then put a fan in front of it and blow it into your face. These humidifiers do not distribute minerals, but they’re pretty good at quickly becoming an unsanitary appliance. Don’t use these. They’re horrible. There really isn’t a situation where you would want to use these at all, anywhere, ever…

“Warm Mist” or “Vaporizor” – These boil the water in one way or another & essentially distill the water as it humidifies. They produce super happy fun time moisture devoid of germs and chemicals. The downside is that over time the heating units get completely encrusted with mineral deposits that must be cleaned off. Some humidifiers have mineral deposit collectors that you can simply swap out & throw away.  Based on my research, and the research of the EPA, these are the best humidifiers to use.