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Naui Nitrox Diver Final Exam 100% A+
Score 2025-2026.
The main reason to dive with "nitrox" is to reduce exposure to some of the problems in diving caused by:
Nitrogen
We say that nitrogen is an inert gas. This means_____.
Our bodies do not use the nitrogen we breathe.
What is the primary safety hazard of breathing nitrogen at depth?
Narcosis
NAUI sanctioned enriched air nitrox training in:
1992
Benefits of nitrox include:
Extended bottom time
Increased safety margins
Shorter surface intervals
The greatest advantages for diving using nitrox occur in what depth range?
15 - 33 msw (50-110 fsw)
True or False: A scuba diver breathing nitrox avoids any risk of nitrogen narcosis.
False
If a nitrox mix is 36% oxygen, what is the fraction of oxygen in the gas mix?
_____ describes the relationship between absolute pressure and the volume of a gas.
Boyle's Law
To find the partial pressure of a gas in a mixture:
Multiply the gas fraction by the absolute pressure.
The water pressure plus atmospheric pressure equals:
Absolute pressure
True or False. Narcosis is reduced significantly when diving with enriched air nitrox.
False
The mechanisms of nitrogen narcosis are thought to be similar to:
Anesthesia
Oxygen is used by the body in:
Metabolism
The term used for low oxygen in the body is:
Hypoxia
Breathing high partial pressures of oxygen can cause:
Convulsions
The accepted oxygen partial pressure exposure limit for recreational nitrox diving is:
1.4 ata
At the first signs or symptoms of oxygen toxicity, a diver should:
Terminate the dive.
Historically, what are the two standard nitrox mixes?
32% oxygen and 36% oxygen
What is the "best mix" to use for an oxygen partial pressure limit of 1.4 ata on a dive to 27 msw (90 fsw)?
EAN
Standard NAUI Dive Tables can be used for altitudes up to about:
300 meters (1000 feet)
NAUI RGBM sea level Dive Tables can be used for altitudes up to:
610 meters (2000 feet)
The NAUI EAN32 and EAN36 Dive Tables have a tolerance of _____ of the tables' value.
+/- 1%
The Rule of Halves is:
For any no-decompression dive, end the dive with a two to three-minute stop at a depth that is half the deepest depth of the dive, followed by a one-minute stop at 3-6 meters (10-20 feet).
All components of the _______ are required for a fire to take place.
Fire triangle
True or False. Silicone lubricants are safe to use with oxygen-cleaned equipment.
False
With regard to oxygen enriched air, as the _________ of oxygen increase, so does the risk of combustion.
Fraction and partial pressure
If contamination of oxygen cleaned equipment is suspected, the equipment must be:
Re-cleaned
Scuba regulators do not need to be specially cleaned for nitrox service unless they will be used with pure oxygen or an oxygen level that is above:
40%
Scuba cylinders that are to contain enriched-air nitrox must be properly cleaned and:
Labled
The continuous flow blending method injects a measured flow of oxygen into the air:
Before it reaches the intake of the compressor.
The simplest method of obtaining precisely mixed nitrox is:
To buy it from a commercial gas supplier.
An essential operation in using an oxygen analyzer is:
Calibrating it.
Most oxygen analyzers use a(n) _________ sensor.
Electrochemical
Verifying the gas analysis and recording it in a fill log is the responsibility of:
The end-user.
True or False: A diver suffering from nitrogen narcosis will know that he/she is suffering
False
The controlled release of pressure during an ascent during SCUBA is called
Decompression
Symptoms of hypoxia begin to appear at what pO
below 0.16 ata
Recommended maximum pO2 for enriched air nitrox diving is?
1.4 ata
First precursor symptom for oxygen toxicity?
Highly variable
Two most commonly used nitrox mixtures, Nitrox 1 and Nitrox 2
32% and 36% oxygen
Maximum operating depth of a gas mix (MOD) is determined by?
Maximum acceptable partial pressure of oxygen
Normal maximum operating depth for EAN 32 with pO2=1.4 ata
34 msw
Best mix to use for an oxygen partial pressure limit of 1.6 ata on a dive to 27 msw
ean 40
Maximum operating depth
Maximum depth dived with a given nitrox mixture
Oxygen percentages on the OCEANx calculator can be set from what?
25%-40%
What is the best mix?
the highest percentage of oxygen that can be used at the planned dive depth
EAN 32, 33 msw, 23 minutes. surface interval: 2 hrs.
10 minutes and 1 hour
If flying or ascending to altitude after diving, wait ______ hours after single dive and _________ hours after series of dives
12 and 18
If using NAUI RGBM dive tables, minimum surface interval of what is required?
1 hour
Petroleum based lubricants are not used with high pressure oxygen because
They may ignite and burn extremely easily
Any equipment that is used with pure oxygen or an oxygen level above ______% must be cleaned for oxygen service
40
Partial pressure mixing
a measured pressure of oxygen is added to a cylinder which is then filled to service pressure with air
Continuous flow method
injects a measured flow of pure oxygen into the air before it reaches the intake of the compressor
Pressure swing absorption
uses a material called a molecular sieve that selectively absorbs a thin layer of nitrogen from the air that passes over or through it
Membrane separation mixing
uses a semi-permeable membrane that allows oxygen to flow through it more readily than nitrogen
An essential operation in using an oxygen analyzer is
calibrating it
An oxygen analyzer should display oxygen content to an accuracy of
1/10 of a percent
When analyzing a nitrox blend the ___________ must be the same as when the unit was calibrated with air
Flow rate
