Ever been to a mercury factory?
I suppose you would imagine people in white suits and breathing masks working behind glassed off areas. Well you would be wrong. Mercury runs down open channels , no masks etc. The difference is that there is adequate ventilation. Chronic exposure to mercury vapours happens in two ways. 1. concentrating the vapour by boiling it. 2. at room temperatures, prolongued exposure over many years. Yes it is toxic, and no, you do not want to injest it or inhale it and minimising the long term exposure of it is a good thing, but please do not go down the scare story of 'one breath and you are dead' routine.