But there is no fire. They just told you some scary stories and did some theatre acting so you believed the building was burning down.

Without even checking for evidence of a fire, you grabbed the nearest fire extinguisher. Upon reading the label you find that the extinguisher is experimental, inside are chemicals that have never tested on a fire before. For some strange reason you decide to shove the nozzle into your mouth and blast the experimental concoction into your body.

That will protect me from the fire, they tested it on 8 mice!

You find that you still caught fire even though there wasn't a fire to begin with. But you are still happy because you would have been more severely burned without the extinguisher chemicals in your body. It could have been a lot worse!