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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. A diver's nitrox computer shows a CNS clock at 75% after the first dive. What should concern the diver most before a second dive?

    Answer: Accumulated CNS oxygen toxicity exposure nearing its limit

    The CNS clock tracks cumulative oxygen toxicity exposure; diving again without adequate surface interval risks reaching 100% and potential toxicity symptoms.

  2. Why does enriched air nitrox reduce a diver's no-decompression limit (NDL) compared to air at the same depth?

    Answer: It doesn't — nitrox extends NDLs by reducing nitrogen percentage

    Nitrox contains less nitrogen than air, so tissues absorb nitrogen more slowly, resulting in longer NDLs for the same depth.

  3. What is the recommended PADI pO₂ limit for normal recreational enriched air diving?

    Answer: 1.4 ata

    PADI recommends a maximum pO₂ of 1.4 ata for recreational diving, with 1.6 ata only acceptable in exceptional circumstances with close monitoring.

  4. A buddy team discovers one diver's cylinder is labeled EANx40 but was only analyzed at EANx36. What is the correct action?

    Answer: Skip the dive and have the cylinder re-analyzed by a qualified technician

    Any discrepancy between the label and analysis requires the cylinder to be re-checked by a qualified technician before it is safe to dive.

  5. Which factor does NOT affect the rate at which a diver accumulates CNS oxygen toxicity?

    Answer: Water temperature

    CNS toxicity accumulation is determined by the partial pressure of oxygen (a function of depth and mix fraction) and exposure time, not water temperature.

  6. A diver using EANx32 plans a dive to 60 feet. Using the EAD formula, what is the approximate equivalent air depth?

    Answer: 47 feet

    EAD = [(1 − FO₂) / 0.79 × (D + 33)] − 33; EAD = [(0.68/0.79) × 93] − 33 ≈ 47 feet.

  7. During a surface interval after an enriched air dive, what happens to dissolved nitrogen in the diver's body?

    Answer: It is gradually eliminated through normal respiration

    During the surface interval, excess dissolved nitrogen off-gasses through the lungs as the body returns toward equilibrium with surface pressure.