Scuba & Nitrox Glossary: M
Nitrox and breathing-gas terminology is prioritized first. General scuba terms follow below. Definitions are educational summaries and do not replace formal training, manufacturer instructions, or an operational dive plan.
Nitrox & Gas Terms — M
- Maximum Operating Depth (MOD)
- The depth at which a gas reaches the selected maximum oxygen partial pressure.
- Membrane Nitrox
- Nitrox produced by selectively removing nitrogen from compressed air through a membrane system.
- Mix Verification
- The process of confirming gas composition, label, cylinder, MOD, and intended use before diving.
- Mixing Stick
- A device designed to mix oxygen and air evenly before gas enters a compressor in continuous blending.
- Molecular Sieve
- Material used in some gas-separation and purification systems.
- Maximum PPO2
- The highest oxygen partial pressure selected for a planned exposure.
- Measured FO2
- The analyzer-confirmed oxygen fraction used for labeling and planning.
- Membrane Feed Air
- Compressed air supplied to a membrane system for nitrogen separation.
- Mix Tolerance
- The acceptable difference between requested and analyzed oxygen percentage.
- MOD Label
- A prominent cylinder marking showing the maximum operating depth for the analyzed mix.
General Scuba Terms — M
- Mask Squeeze
- Barotrauma caused by failure to equalize the mask during descent.
- Minimum Gas
- The calculated gas needed for two divers to manage an emergency and reach a safer point or the surface.
- Multilevel Dive
- A dive conducted at more than one depth, usually moving shallower over time.
- Mouthpiece
- The part of a regulator, snorkel, or rebreather held in the mouth.
- Mooring Line
- A line securing a vessel to a mooring.
- Marine Protected Area
- A region managed to protect marine habitat, species, or cultural resources.
- Mask Strap
- The adjustable band that holds a mask in position.
- Maximum Depth
- The deepest point recorded or planned for a dive.
- Modified Flutter Kick
- A compact flutter kick used to reduce bottom disturbance.
- Muck Diving
- Diving over sand, silt, or rubble to find small or unusual marine life.