It suck the air from the barrel, but where you think the air then go? They claim "mercury filters", but what about the mercury vapor (in normal room temperature it exceed safe concentration more then ten times)? Filters are able to catch only non-gaseous substances, so only dust and droplets, but the vapor might pass very easily. Moreover mercury gas, even if heavy, has quite small particles - they are single atoms, so about the same size as O2 or N2 molecules, so there is no filter capable to catch them from the air (except cold condensation traps, but i didn't noticed these machines having chiller machinery necessary for such functionality)...
