sszalay

I remember hearing an inspector on a web video (though I can't find it now) say that the heating duct in a newly finished basement that comes down through the external wall, through the top plate, of a steel studded wall, has to have "cold air ground and firestop bonded." I have a similar situation in a basement I'm doing and I know what firestopping is, but I can't find anything on "cold air ground". Can someone point me in the right direction. I'd appreciate it. Thanks.