Grey flakes in my humidifier?
October 2, 2006 10:46 PM   Subscribe

What are these grey/black flakes coming out of my humidifier?

I bought a cheap Kaz warm steam vaporizer a year or two ago, and every time I go to the sink to refill it, I find a large amount of dark grey flakes on the bottom of the water reservoir. I've tried rinsing the steam unit itself, and no matter how much I rinse it out, more black flakes will come out of it.

3 questions:
1) What are these flakes
2) How does this finite-mass object produce an infinite supply of black flakes
3) Can I get rid of them once and for all by doing something like dumping ammonia or vinegar or CLR into the steam unit?
posted by anonymoose to Technology (9 answers total)
If the supply is unlimited, it's probably biological. Mold or mildew?

You could probably try a weak bleach solution.
posted by Malor at 10:53 PM on October 2, 2006

Dont worry about it. Happened to me too. I also used Google with words such as "humidiifer black flakes" which will return info such as:

A Vaporizer produces moisture by heating small amounts of the minerals in the water using tiny electrodes in the shaft of the unit. The minerals then heat the water to a boil and release steam into the air. The minerals will then settle to the bottom of the tank, possibly becoming small black flakes. These flakes are normal and should be rinsed out when you refill the tank.
posted by vacapinta at 11:05 PM on October 2, 2006

Exactly. Why wouldn't precipitation of dissolved solids be the first thing you think of? Then again, the OP seems to have a history of asking easily-googleable questions.

Now, since the machine works by passing a current through the water, what do you think would happen if you washed it out good and added distilled water?

I take no responsibility for anything that happens as a result of trying this.
posted by Mr. Gunn at 5:56 AM on October 3, 2006

Best case scenario (and most likely): bits of activated charcoal or the like from the filter (harmless, but annoying).

Worst case scenario (but highly unlikely): Stachy.

Middle-of-the-road case scenario: Other mold or biological agents.

If it really bothers you, see if the retailer or manufacturer will take it back.
posted by fvox13 at 6:31 AM on October 3, 2006

fvox13, you're absolutely wrong in all three scenarios. Moreover, the correct answer was posted just upthread.
posted by Mr. Gunn at 6:40 AM on October 3, 2006

yeah, it's dissolved minerals precipitating out. The colour depends on what kind of minerals are in your water. Mine always used to be grey/white.
posted by GuyZero at 6:41 AM on October 3, 2006

The text vacapinta came across implies the water is heated by passing a current through it directly; if that's the case, your humidifier won't work with distilled (ion-reduced) water, which is a pretty good insulator.

I think it's much more likely your humidifier heats the water by passing current through a heating element like the one in your water heater, only smaller. This element has a nichrome wire embedded in heat-resistant insulating powder, all inside a metal jacket which will resist corrosion.

I think the flakes do have a lot of dissolved mineral, but if that were all, the flakes would be white or very light gray. The black is metal oxide coming from the element, I believe, and you might be able to minimize it by keeping the humidifier full, and dumping out the water and refilling it instead of topping it up. This will have the effect of keeping the element submerged, which will reduce surface oxidation because that's worse in air, and it will reduce precipitation of minerals too, because they won't build up so much.
posted by jamjam at 12:35 PM on October 3, 2006

The Kaz product in question DOES work by passing current directly through water. I have a similar unit made by Vick's and get similar black flakes. Not sure what's precipitating out of the water, but there you go.

And no, they don't work with distilled water. You have to add salt (or a similar mineral) if you have relatively soft tapwater.
posted by mmoncur at 5:07 AM on October 4, 2006

Thanks for that information, mmoncur!

That seems like a really hard way to go. I wonder what the electrodes are made of? Probably not Platinum or Palladium, I'm thinking. Old dry cells used a carbon electrode...

One of the things that surprises me about this is that it would seem very likely to generate various oxides of chlorine from the combination of oxygen from electrolysis and chloride ions from the salt (which is an effect exploited by some water purifiers for their disinfectant properties) one of which is the hypochlorite, which is ordinary laundry bleach. Do these humidifiers smell at all like bleach?
posted by jamjam at 1:10 PM on October 4, 2006

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