Underwater diving uses self-contained underwater breathing apparatuses (SCUBA) that allow divers to breathe underwater independently of surface supply. SCUBA systems include high-pressure diving cylinders that hold compressed air or gas mixtures, and one- or two-stage regulators that reduce cylinder pressure and deliver breathing gas on demand to the diver. While early regulators were single-stage, modern two-stage regulators have become popular as they deliver air more reliably during inhalation.

1. Underwater diving
Marco Renzelli

2. S.C.U.B.A.
• Self
• Contained
• Underwater
• Breathing
• Apparatus

3. How to breathe underwater
• The diving regulator:
• Diving cylinders(200-300 bars)
• 1 stage regulator
• 2 stage regulator

4. Diving cylinders

5. 1 stage regulator

6. 2 stage regulator, the
demand valve

7. The past: the old diving
regulator, 007’s era

8. The future: the rebreather?