NEVER try to pick up hot glass bare handed when carrying out Glass-blowing operations NB Hot glass looks EXACTLY like cold glass
Never sniff a flask you suspect may contain Ammonia, the resulting recoil and fall backwards over several Lab stools can cause much hilarity amongst colleagues.
On a serious note NEVER do mouth to mouth on anyone you even suspect may have inhaled a noxious or toxic gas, You could join them unconcious on the floor, This applies to Houshold as well as Chem lab accidents , ie Bleach inhalation, Car exhaust fumes etc.