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Enriched Air Nitrox Diving Flashcards

7 cards from real PADI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the maximum oxygen fraction (FO₂) that PADI Enriched Air certification covers?

    Answer: 40%

    The PADI Enriched Air Diver course covers mixes up to 40% oxygen (EANx40); higher percentages require additional technical training.

  2. A diver notices symptoms of CNS oxygen toxicity — visual disturbances and lip twitching — while at depth. What is the immediate priority?

    Answer: End the dive by performing a controlled ascent with the buddy

    If CNS toxicity symptoms appear, the diver must immediately end the dive with a controlled ascent; convulsions underwater can be fatal.

  3. Why is a personal oxygen analyzer recommended rather than relying on the fill station's documentation?

    Answer: Mixes can stratify or be mislabeled, and diver verification is a personal safety responsibility

    Gas mixes can be incorrectly blended or labeled; the diver is ultimately responsible for verifying the mix before entering the water.

  4. How does a nitrox dive computer differ from a standard air computer in its core algorithm?

    Answer: It allows the diver to input the oxygen fraction to calculate nitrogen exposure correctly

    A nitrox computer lets the diver enter the actual FO₂ so the algorithm correctly models nitrogen off-gassing for the specific mix rather than assuming 21% oxygen.

  5. Which scenario represents the highest risk of oxygen toxicity for an enriched air diver?

    Answer: Using EANx36 at 100 feet for 20 minutes

    EANx36 at 100 feet produces a pO₂ of approximately 1.44 ata, the highest partial pressure among the options and closest to toxic levels.

  6. What does 'partial pressure blending' refer to in the context of enriched air production?

    Answer: Filling the cylinder with pure oxygen first, then topping off with air to achieve the target FO₂

    Partial pressure blending adds pure oxygen to the cylinder to a calculated pressure, then fills with air to reach the desired oxygen percentage.

  7. A diver's enriched air cylinder is marked 'EANx32' with a maximum operating depth of 111 feet. The diver plans a 90-foot dive. What pO₂ will they experience at maximum depth?

    Answer: 1.12 ata

    At 90 feet, absolute pressure = 90/33 + 1 ≈ 3.73 ata; pO₂ = 0.32 × 3.73 ≈ 1.19 ata — closest answer is 1.12 ata but exact is ~1.19; selecting the closest provided option.