I once used to work in a bookshop and we had an attack of tiny fruit flies or something that came in a container/box or something. Anyway, on my lunch break, I emptied a bottle of bleach into the central airconditioning and by mid afternoon the entire staff and customers had weepy eyes and couldn't breath. I pretended I was ok despite feeling lightheaded and wanting to vomit and when they began to ask each other frantically, I denied anything felt wrong. I was about 15 or 16 at the time and nervous about getting caught out.

The fruit flies died.