Fire ratings such as A60 and H120 indicate the duration the doors and walls must be able to withstand a particular type of fire.
Difference between A- and H-fire ratings
A-fire rated doors and walls are tested with a ISO cellulosic fire temperature curve. H-fire rated items are tested with a hydrocarbon fire curve. The hydrocarbon fire curve has a faster build-up and higher plateau temperature than the standard A-curve.
The fire doors and fire walls shall maintain their function with respect to fire resistance and structural integrity when exposed to a heat load characteristic for cellulosic (A-fire rating) fire or hydrocarbon (H-fire rating) fire.