Hey! I finally finished the garage bedroom/office space and everything went pretty well, save for a few minor details. Last thing now is to run the ducting for A/C and heat into the room. I've got 6" flex duct rated at 200 degrees F that I plan on connecting via a T-connector from the bathroom ducting nearest the garage. My brother-in-law, formerly a sheet metal man who worked on high rises, advised me to install a metal firewall collar into the firewall from the garage attic leading into the house attic where the FAU is. He said there's an apparatus that features a trap that shuts automatically in event of fire, sealing the ducting hole...is this necessary??? if not, I located a metal collar/flange called a "firewall collar" that looks like two of 'em would act as a grommet in the hole I will cut through the firewall...would that suffice?