The no decompression limit or NDL is a term used in the PADI dive tables for scuba diving to indicate the maximum amount of time that can be spent at a given depth underwater, before the diver has absorbed enough nitrogen gas into their body tissues to be susceptable to decompression sickness.
This limit varies not only with the depth and time underwater, but also with any residual nitrogen the diver may have picked up in previous dives.
If the diver exceeds the no decompression limits, as laid out in the PADI recreational dive tables, for any more than three minutes, the diver should ascend to a depth of 15 ft. (5 m) and wait for a minimum of 3 minutes before surfacing. If symptoms of decompression sickness are evident after surfacing, seek attention from medical personel.