Apprentice question
Stop and ask
Stop. Get direction before you touch it.
A wide open floor penetration is a rated-assembly problem. Stop and firestop/sleeve it only by the approved listed detail.
['A slab opening around duct is not just an ugly hole. It can pass smoke, fire, noise, and air between floors if it is not sleeved and firestopped correctly.', 'Document the gap, confirm whether the floor is rated, and coordinate the approved sleeve/firestop/wrap/mineral wool/intumescent system before covering or turnover.']