ENRICHED AIR NITROX FREQUENTLY TESTED
ACTUAL EXAM QUESTIONS WITH CORRECT
ANSWERS (2026)
●● How is the ppO2 of a breathing gas calculated?
Multiply cylinder pressure by the fraction of nitrogen (FN2) in the
cylinder
Multiplying ambient pressure by the fraction of oxygen (FO2) in the
breathing gas
Dividing ambient pressure by the fraction of oxygen (FO2) in the
breathing gas
Multiplying air pressure by the fraction of oxygen (FO2) in the breathing
gas
Answer: Multiplying ambient pressure by the fraction of oxygen (FO2)
in the breathing gas
●● What does ppO2 mean?
Nitrox
Air
Partial pressure of oxygen
Partial pressure of nitrogen
, Answer: Partial pressure of oxygen
●● The threshold for CNS oxygen toxicity appears to be at a ppO2 of:
1.4 ata
1.6 ata
1.1 ata
32%
Answer: 1.1 ata
●● The risk of CNS Oxygen Toxicity becomes more substantial above:
A ppO2 of 1.6 ata
A dive time of 30 minutes with air at 66 feet
A ppO2 of 1.4 ata
1000 feet of altitude
Answer: A ppO2 of 1.6 ata
●● Pulmonary Oxygen Toxicity (the Lorrain Smith Effect) poses no real
risk to recreational divers because:
Pulmonary Oxygen Toxicity does not lead to problems.
ACTUAL EXAM QUESTIONS WITH CORRECT
ANSWERS (2026)
●● How is the ppO2 of a breathing gas calculated?
Multiply cylinder pressure by the fraction of nitrogen (FN2) in the
cylinder
Multiplying ambient pressure by the fraction of oxygen (FO2) in the
breathing gas
Dividing ambient pressure by the fraction of oxygen (FO2) in the
breathing gas
Multiplying air pressure by the fraction of oxygen (FO2) in the breathing
gas
Answer: Multiplying ambient pressure by the fraction of oxygen (FO2)
in the breathing gas
●● What does ppO2 mean?
Nitrox
Air
Partial pressure of oxygen
Partial pressure of nitrogen
, Answer: Partial pressure of oxygen
●● The threshold for CNS oxygen toxicity appears to be at a ppO2 of:
1.4 ata
1.6 ata
1.1 ata
32%
Answer: 1.1 ata
●● The risk of CNS Oxygen Toxicity becomes more substantial above:
A ppO2 of 1.6 ata
A dive time of 30 minutes with air at 66 feet
A ppO2 of 1.4 ata
1000 feet of altitude
Answer: A ppO2 of 1.6 ata
●● Pulmonary Oxygen Toxicity (the Lorrain Smith Effect) poses no real
risk to recreational divers because:
Pulmonary Oxygen Toxicity does not lead to problems.
