I have a player who wants to buy crazy purple knock-out gas. I told him there is neuro-stun gas he can purchase. I told him his fixer needs to find out who has it to buy me some time on the subject. I think the core books states that it cost 65. I not sure how it is used, how much 65 buys you, and how big a room can big affected? Any advice?

the only method i am aware of (so far) of distributing gases would be via the gas grenade. i would say 1 dose should be enough to fill one gas grenade, IMO.

of course, if you want to make some stuff up, then go ahead.