When cable trays pass through walls or floors, seal openings using fire-rated penetration sealing materials. Do not modify or damage the tray coating or structure during use. The following charts give the number of 3M pillows needed to completely firestop an opening that cable tray passes through. UL Listed Systems Concrete Wall - C-AJ-4056 3 HR F-Rating, 3/4 HR T-Rating Gypsum. These intumescent urethane foam blocks are installed in openings by compressing and stacking into the opening in a brick-like fashion. It was as if a different person planned and executed each and every hole — even in the same building, even on the same floor! There.
