Fire rated door has different design for different building types.
In the construction of fire rated doors design, should be in accordance with the nature of the building, type, in strict accordance with fire technical specifications, reasonable fire rated doors, and not arbitrarily reduce the fire rated door grades.
Grade 0: no defined corrosion resistance
Grade 1 or A: mild resistance
Grade 2 or C: moderate resistance
Grade 3: high resistance
Grade 4: very high resistance