Under what conditions is a 3-minute safety stop at 5m/15ft required for divers?

A 3-minute safety stop at 5m/15ft is recommended to help divers mitigate the risk of decompression sickness, especially after deep or prolonged dives. The correct response indicates that this safety stop is essential when a diver has exceeded a depth of 100 feet or has concluded a dive within three pressure groups of their no-decompression limit. Diving deeper than 100 feet increases the likelihood of nitrogen absorption in body tissues, which can lead to a higher risk of decompression sickness.

By staying at this shallow depth for a safety stop, divers allow the excess nitrogen time to be eliminated from their bodies, which helps prevent the formation of nitrogen bubbles that can cause DCS. Additionally, the reference to pressure groups reinforces the importance of adhering to dive tables or computer limits, as proximity to the no-decompression limit means that a diver's body is under greater pressure and nitrogen levels are elevated.

In contrast, not all dives necessarily require a safety stop; thus, having a stop after every dive, diving beyond 120 feet, or after a dive lasting more than 60 minutes do not specifically correlate with the established guidelines that necessitate a safety stop as indicated in the correct choice. Each of these scenarios may have their own safety protocols, but