I would have to say that one of the most difficult discussions that occurs in the world of HVAC is fire/smoke codes and safety issues. Every situation seems to take on it's own life with new questions arising all the time and there seem to be so many issues not yet addressed. Don't be a dummy when it comes to Fire/Smoke safety, register for Ruskin's October 12th Webinar. http://www.ruskin.com/NewsArticles/entryid/725/free-webinar-ruskin-fire-smoke-damper-product-code-update