The higher the rating, the safer the safe. “TL 30 x 6” refers to a safe where all six sides of the safe were attacked.
A “TRTL 30” rating designates a safe that successfully resisted 30 minutes of net working time with a torch as well as the tools already noted.
A fire-resistant safe is designed to withstand high temperatures and protect the items stored within. They are also often engineered to be impact resistant, i.e., they can survive being dropped from a considerable height.
The impact resistance is considered because, during a fire, floors burn and collapse, taking the contents down with them.
UL tests fire resistance by heating a safe to an external temperature of 1,500 degrees Fahrenheit and then measuring how long it takes for the interior temperature to rise to 350 degrees Fahrenheit.
It chose 350 degrees Fahrenheit because paper begins to char over 400 degrees.
A safe with a “Class 350 1/2 hour fire rating” will maintain an internal temperature of less than 350 degrees Fahrenheit for a half hour.
For impact testing, UL heats the safe up as it does with fire testing and then drops the safe onto concrete rubble from a height of 30 feet. It then turns the safe upside down, reheats it, and drops it again.
Throughout this testing, the safe must maintain its integrity and protect its contents. A safe with a “Class 350 1 hour fire and impact” label will have passed both tests and protect the safe’s contents for one hour.