What key factor determines the amount of time a diver has to surface without risk of decompression sickness (DCS)?

The amount of time a diver has to safely ascend to the surface without the risk of decompression sickness (DCS) is primarily determined by the diver's depth and previous dive profile. When a diver descends to greater depths, the partial pressure of gases, particularly nitrogen, increases in the body’s tissues and blood. The deeper and longer the dive, the more nitrogen is absorbed.

As the diver ascends, it is crucial to control the rate of ascent and include safety stops to allow for the gradual elimination of nitrogen from the body. If a diver ascends too quickly, dissolved nitrogen comes out of solution too rapidly, leading to the formation of bubbles which can cause DCS. Therefore, understanding the specifics of the dive profile—depth, duration, and any previously completed dives—is essential in determining the safe ascent protocol and avoiding DCS.

While factors such as a diver's experience, water temperature, and type of diving equipment can influence safety and comfort, the critical element that dictates the physiological response to pressure changes and nitrogen absorption is indeed linked to depth and dive history.