Has anyone built or even know what the piece of equipment that venkman has in dana’s apartment for the first time? I haven’t seen any plans of it or comments on what it actually detects or does. Please someone fill me in.
http://www.gbfans.com/equipment/other/bacharach-sniffer/ 
I believe irricanian and a few others have made them! 
http://www.questvideoproduction.com/GhostSniffer.html
http://www.gbfans.com/community/viewtopic.php?f=7&t=4671
there’s a great “how to” and a good discussion on it.