Isolation of caffeine from tea bags?

I did a lab where we isolated caffeine from tea bags using extraction, drying, evaporation , and sublimation. I wanted to know what would happen to the caffeine if the sublimation step was performed at atmospheric pressure?Isolation of caffeine from tea bags?
It would have sublimed if it did not decompose. You pull a vacuum during distillations and sublimnations to make the temperature you need to achieve lower. Excessive heating of a compound often leads to decomposition.