Maximum allowed gap for fire stopper between floors
I just install a new duct. Inside the main riser (supply), between floors, I put a cut out piece of metal. However, there is always a gap between the metal and the riser or between the metal and the surrounding area. I saw there is no further insulation other than the metal sheet for the existing flu. My question is what is the maximum allowed gap between the firestopper metal sheet and the riser.