We are not sure where this myth started but contrary to popular belief, tapes, external hard drive and other backup media is not safe in fire proof safes.
Fire proof safes are meant to protect paper form catching on fire and that’s it. If you have a 5 hour fire proof safe what that means is that when the safe is in a fire, the paper contents in it will not catch on fire for 5 hours. What these safes do is protect their paper contents form reaching a specific temperature, the flash point of paper, for a specific time. Unfortunately, tapes, hard drives and other backup media will be destroyed long before the flash point, or combustible temperature of paper is reached.