Last week Kelly Berger, the Store Director for COSI, stopped me in the hallway. Apparently they had been getting some comments. There's a towering display in the gift shop full of Himalayan Salt Lamps, which promised that the lamps would "emit negative ions" to "remove impurities from the air". I'm sure the comments went somewhere along the lines of "uh...are you....are you sure?"
Salt is made of two elements stuck together: sodium and chlorine. This connection is pretty strong, and they only tend to separate in things like water. Making...you guessed it...salt water. If you heat up a block of salt enough to vaporize it, the negative ions of chlorine* and positive ions of sodium** just find the nearest water molecule floating in the air and hitch a ride.
So assuming the lamp is hot enough to even do anything interesting to the salt (and it probably isn't, because it's just a light bulb), the only thing it would make is slightly salty air.
I'm glad Kelly came to me. If you search online almost all the links are to horrible sources, so it's hard to tell what's really going on. And I don't object to selling the lamps as lamps. They look nice and fit in with the other gem and mineral doodads we sell.
However, this concept of magical healing/cleaning properties from Himalayan*** Salt Lamps isn't grounded in much actual science. I'm sure that turning on a cozy light and chilling out has health benefits, but it ain't the salt that's doing it.
*Fun fact: If this device actually emitted pure negative ions from salt, it's spitting out chlorine gas, which is a deadly deadly poison.
**Bonus fun fact: Sodium by itself is highly reactive, which is a fancy way of saying "explosive". So remove all the chlorine from salt and...boom.
***Extra credit fun fact: Despite the name, they're usually from Poland.