This didn't happen to me personally, but it still made me wince.
Several years ago, the chemical company I work for used formaldehyde as a preservative in a few of its products. As it's solid/very gloopy at room temperature (depending on the supplier), formaldehyde is not easy stuff to handle, so on the plant it was kept in heated vessels and pumped around in its hot, fluid state. Which was all very well and conformed to safety standards, until one of the pipes started leaking.

The first person to notice the leak was a lad not over-endowed in the common sense department; he went right up to the hissing, steamy brown trickle to get a good look, put his foot directly underneath, and got a nasty surprise as it burned right through his safety boot, made short work of his sock, and settled into his toes. Having withdrawn his foot and spent some time hopping around screaming blue murder, he then took off his boot and took a good deep sniff of his now-blackened toes. At which point he passed out from the fumes and hit his head on the smooth, tiled floor.

In the end, three of his toes were so badly burned they had to be amputated, and for various reasons including but not limited to this incident, formaldehyde was completely phased out within the following year.
( The Mock TurtIe ™ --- Thinks you are a cunt, on, Sun 1 Aug 2010, 22:03, 1 reply)

Nasty stuff that.
I remember stinking the lab out when making small quantities of that and ammonia as a decomposition product of hexamethylenetetramine. Fun times.
( Colonel Boris "...a desperate Buzzfeed imitation...", Sun 1 Aug 2010, 23:31, closed)