Matthew, Being one of those "die-hard smokers" I feel obliged to help my fellow outcasts! I suggest you get your hands on a book: Industrial Ventilation American Conference of Governmental Industrial Hygenists Lansing, Mi. Ph: 513-661-7881 Library of Congeress Cat Card No: 62-12929 It's written in plain english, with "Do this, or this, but never that" type illustrations. I've been very pleased with this valuable resource for all sorts of building and equipment ventilation issues I've confronted. Good Luck, Ed Popielarski QTA Machine 10 Mc Laren, Ste. D Irvine, Ca. 92618 Ph: 949-581-6601 Fx: 949-581-2448 http://www.qta.net Check out our BGA Baller and Process Equipment Services!