This thing adapts a standard 12cm PC fan to a standard 4" exhaust / vent duct (available a Lowes or HD). This allows smooth flow of fumes to wherever you like (outside).
Once again, I had this all typed out and lost it when I uploaded pic. Crap.
Basically, print out thing 4 times, cut/trim excess plastic and/or raft.
Screw pieces to standard 12cm fan (120mm).
Seal part gaps with hot glue (recommended).
Connect other side of fan to a board (cardboard for me), and attach to side of makerbot. Be sure to enclose the box a much as possible (I leave the front of mine open for good air flow)
Now I can print 24/7 without having to worry about inhaling fumes.