What is decompression in diving?

Decompression is the release of the inert gas, mostly nitrogen, that your body absorbs while breathing under pressure. The deeper and longer the dive, the more nitrogen dissolves into your tissues. On the way up it has to come back out, and it must come out slowly enough to stay dissolved instead of forming bubbles. In that sense every dive is a decompression dive: a controlled ascent rate is decompression happening in real time.

Do all dives require decompression stops?

No. Most recreational diving stays inside the no-decompression limit (NDL): the time you can spend at a given depth and still ascend directly to the surface at a safe rate. Exceed the NDL and you take on a decompression obligation — mandatory stops at set depths where you wait while your tissues off-gas. Those stops cannot be skipped, which is why deco diving demands dedicated training, planning and reserve gas.

What is decompression sickness?

Decompression sickness (DCS) occurs when the ascent outpaces the off-gassing and bubbles form in tissues and blood. Symptoms range from joint pain, unusual fatigue and skin rashes to numbness, weakness and, rarely, life-threatening neurological injury. It is uncommon in divers who ascend slowly and respect their limits — that ascent discipline exists precisely because of DCS. Treatment is first-aid oxygen and recompression in a hyperbaric chamber.

How do divers manage decompression in practice?

• Dive computer — tracks depth and time continuously and shows your remaining NDL or required stops.
• Slow ascent — around 9–10 m per minute or slower, especially near the surface.
• Safety stop — three minutes at 5 m on every dive; optional on paper, standard in practice.
• Richer mixes — technical divers switch to high-oxygen mixes or pure oxygen during deco to speed up off-gassing.