You can fiddle with those concentrations that will kill people in a room from the fumes themselves - if you want (and it will be your last time ... :-) ... ) — but I’m staying away from it 100%
It ranges from from a few drops killing you, to just one drop killing you, to fumes killing you — all on the basis of concentration levels — ranging from a 10 or 20% level to a 80% or more.
Here’s a highly concentrated form ...
http://www.e-cig.com/e-liquid-pure-nicotine-240ml
It would seem to me that a whole room of consensual e-smokers could just vaporize this stuff in the room and forget their individual e-ciggies.