Fume cupboards work pretty well. If you leave the fan running I think all the airflow is in and up the chimney. I presume Bohr would have used one.
(Just got side tracked reading about old style fume cupboards http://www.cf.ac.uk/estat/sustainability/initiatives/ )
I love how diverse HN can be. From Ph.Ds in computer science to former jewelers, there seems to be a little bit of everything.
Follow up question: would the gas have stuck around until the Nazis arrived a while (hours or less?) later? Or would their ventilation have dispersed it enough?
I remember in the science classes I took in HS the ventilation hoods pretty much removed most of the fumes, but we also never worked with anything that was particularly... pungent? My last science class was probably 5 years ago, so that's my level of understanding.