One of the top reasons people choose to purchase a safe is for the fire protection they offer. You can get anywhere from 30 minutes to 2.5 hours of fire resistance for your firearms and valuables.
The main goal is to keep the inside temperature of your safe low, for as long as possible. The longer time ratings will ensure the contents of your safe will be exposed to less heat for a longer time.
The construction of a safe is what determines fire protection.