Nitrogen dioxide

[Julian]

A compound of nitrogen and oxygen formed by the oxidation of nitric oxide (NO) which is produced by the combustion of solid fuels.

[Justin Bieber]

[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 doesnt 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 ones 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.

[Renato]

a poisonous brown gas, formed when some metals dissolve in nitric acid