When you expect it. I was at a grocery chain here in Canada called 'Superstore' and I was walking by the misters when they went off, but the one beside me didn't. Like an idiot I moved in and examined the mister.

Nothing happened. I turned away and started looking at products in the other direction.

That is when whatever had dried on the nozel had partially shot off and hit me in the back along with the mister soaked my back from my head to the top of the butt of my pants.

It was -43°C outside.