I just finished re-drywalling my kitchen ceiling. I cut out for the electrical box and I got pretty close but there is still a considerable half inch gap most of the way around, and wider at the corners. Here's a picture of the box:
I bought two 3M fire caulks, FB-136 (gray) and CP-25WB+ (red). CP-25WB+ is "intumescent" meaning it expands if there's heat. FB-136 is "versatile" which I assume just means versatile. Other than that I don't see much difference except some code compliance (detailed below). Here's a picture of the caulks:
My questions are
Should I fill in that gap between the electrical box and the drywall? I would assume so to prevent against fire right? There is no insulation in the kitchen ceiling.
If yes should I use fire caulk? My concern with that is I assume it will eventually it will become brittle and could fall down from the gap into whatever lamp fixture I'm putting up there, and it could actually create the very hazard I'm trying to prevent.
And also which fire caulk? Why would you use one over the other? The FB-136 gray says it is current to ASTM E136, IBC2003, IRC2003, IRMC2003, IRFGC2003, NPFA 5000. The CP-25WB+ says none of that but it expands on heat contact.