Does a 1 hour fire resistant door really only last 20 minutes before it burns up in fire?
No. A fire resistance rating is determined by the amount of time
a partition will prevent the spread of fire, so a one-hour door
(and its wall and supports) would have to hold back a typical fire
growing for at least one hour. For example, a 20-minute fire rating
requires a fire door to withstand an intense fire on one side,
rising to over 1,400 degrees F during twenty minutes, and then
being hit by a pressurized fire stream, without causing any