If you accidentally exceed the maximum dive time, you are required to perform a decompression stop. This is a dangerous situation because missing the stop for any reason can lead to decompression sickness.

Your blood and tissues absorb nitrogen faster when cold, so for increased safety, round your dive time up to the next greater time if you become chilled during a dive.

Your body ingasses nitrogen faster at deeper depths than shallower depths, but it also begins offgassing a significant amount of that nitrogen when you ascend to a shallower depth.

Your maximum dive times at high altitude are lower than at sea level. To dive at altitudes higher than 1000 feet, you must use special tables designed for altitude diving or a dive computer equipped with an altitude compensation feature.