Silicone is not suitable for this application because it will only dry out and become useless after exposure to heat or flames which could lead to an even greater threat than if there were nothing present at all. It's important to remember that what separates firestop sealant from regular old silicone caulk is its ability to withstand extreme temperatures without becoming compromised by them- both hot and cold! Firestop caulking is specially formulated to meet the standards set by ASTM E-84 for fire safety.