On pre fab firplaces with the knockout on the side for a gas line, is it required to seal the area around the gas line.I always call these out to be sealed.Seems like I read that somewhere.Recently while inspecting new homes I have not seen where this area is sealed.It is so prevalent that this area is not sealed I have started to question if I'm correct for calling it out.I have gone to manufacturers installation pages where it is not mentioned. Danny Pritchard