Nitrogen dioxide, or NO2, is a brown, highly toxic gas that can be produced by the oxidation of nitrogen (for example, combustion reactions produce NO2 and other oxides of nitrogen, as some of the oxygen reacts with nitrogen in the air) and the reaction of concentrated nitric acid with some metals (examples include copper, silver, and magnesium).

Even in extremely low concentrations, the slightest whiff of NO2 will have the same effect on your nasal cavity that Drano has on a clogged sink. Its odor doesn't have a 'flavor' to it, per se, but rather exists as a sharp burning sensation akin to the feeling of having a mixture of wasabi and fire ants shoved up one's nose.

Nitrogen dioxide is not to be confused with nitrous oxide, which is more commonly known as laughing gas, and has the formula N2O. Confusing one for the other can often result in fatal consequences.
Cu + 4 HNO3 ——> Cu(NO3)2 + 2 NO2 + 2 H2O

Jim: Hey Steve, wanna go get high off some nitrogen dioxide?
Steve: Uh, don't you mean nitrous oxide?
Jim: Nah dude, it says here on the container, "NO2." You think I don't know basic chemistry?
Steve: Whatever man, count me out.
Jim: More for me, then!

*later, Jim is found lying in a pool of blood, having died of severe hemorrhaging from his lungs and respiratory tract*
by Necropolitan October 27, 2011
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