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Glossary - N

N2 Nitrogen
NACD  National Association of Cave Divers
Narcosis The intoxicating effects of breathing inert gases, such as Argon, Nitrogen or Hydrogen when the diver is exposed to elevated partial pressures at depth. The condition is generally alleviated upon ascending, or by changing the mixture ratios to reduce the partial pressure of the offending gas.
Narcs Nitrogen Narcosis.
NAUI  National Association of Underwater Instructors
Nautical mile Unit of distance equal to one minute of latitude. 1n.mile = 1.852 km
Navigation The science and art of  conducting a dive or a boat safely from one point to another.
NDL No Decompression Limit - the maximum time one may stay at a particular depth in order to avoid decompression diving.
NDO  National Diving Officer
Neap tide These tides are neither very high nor very low (the tidal range is small) and occur when the sun and moon are pulling against each other at the first and final quarters of the moon.
Neon A gas sometimes used in diving.
Nitrogen A gas that makes up approximately 78% of the air we breathe. It is usually the gas responsible for DCS when diving on compressed air. It also caused Narcosis from about 30m
Nitrogen Narcosis Loss of judgment and motor skills caused by the narcotic effect of breathing the nitrogen component of any breathing gas at elevated partial pressures (i.e. at depth). The condition is alleviated upon ascending. Also known as "Rapture of the deep" or "narcs". Nitrogen narcosis, a common form of inert gas narcosis, can be incurred at depths as shallow as 30m, and possibly even shallower by individuals who are more susceptible.
Nitrox Literally, any breathing gas consisting of a mixture of Nitrogen and Oxygen. Generically referred to when the Oxygen percentage in the mix is in the range of 21-50%. In diving,
NMR The National Monuments Record. A public access database maintained by English Heritage and recording details of historic monuments throughout the UK. The maritime section of this database is maintained by the Royal Commission on the Historic Monuments of England (RCHME) and records wreck sites and artefacts from a maritime context around the coast of England and dating to pre-1945.
NOAA National Oceanic and Atmospheric Administration (U.S.).
Normoxic A breathing mixture that yields a partial pressure of Oxygen at normal (.21bar) levels.
No Stop Dive A dive in which there are no decompression or "offgassing" stops
NQI  Nationally Qualified Instructor.










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