ADCI Surface Supplied Mixed Gas Diver Certification Exam
Questions and Answers
1. What is the primary purpose of using mixed gas (e.g., heliox) instead of air for deep diving?
Answer: To reduce both nitrogen narcosis and the risk of oxygen toxicity.
2. Which gas mixture is most commonly used for deep surface-supplied mixed-gas diving?
Answer: Heliox (helium-oxygen).
3. What is the maximum allowable depth for surface-supplied air diving per ADCI standards?
Answer: 165 fsw (50 msw) in some contexts, but typically limited to 130-165 fsw depending on
operations.
4. What is the primary hazard associated with high partial pressures of oxygen in mixed-gas
diving?
Answer: Central nervous system (CNS) oxygen toxicity.
5. What is the maximum operating depth (MOD) for a helium-oxygen mix with 2% oxygen?
Answer: Calculated using PPO2 = 1.6 ATA (e.g., MOD = (1.6 / FO2) - 33 fsw).
6. According to ADCI, what is the minimum oxygen percentage required in breathing gas for
mixed-gas diving?
Answer: 0.16 ATA (16% at surface).
7. What is the main function of a dive bell in mixed-gas operations?
Answer: To provide a controlled decompression environment and emergency refuge.
, 8. Which regulator is typically used in surface-supplied mixed-gas diving?
Answer: Demand regulator with non-return valve.
9. What is the primary advantage of using helium in breathing mixtures?
Answer: Reduces nitrogen narcosis.
10. What is the recommended maximum PPO2 for mixed-gas diving to avoid CNS toxicity?
Answer: 1.6 ATA.
11. In mixed-gas diving, what is the primary cause of high-pressure nervous syndrome (HPNS)?
Answer: High partial pressure of helium at extreme depths.
12. What is the minimum ventilation rate for helmets/masks in mixed-gas operations?
Answer: 4.5 ft³/min at operating depth.
13. What must be present at the dive site for mixed-gas diving deeper than 130 fsw?
Answer: Decompression chamber.
14. What is the color coding for helium cylinders per ADCI standards?
Answer: Brown with white shoulder.
15. What is the purpose of a non-return valve on the diver's umbilical?
Answer: Prevents loss of gas if umbilical is severed.
16. What is the maximum allowable CO2 in breathing gas?
Questions and Answers
1. What is the primary purpose of using mixed gas (e.g., heliox) instead of air for deep diving?
Answer: To reduce both nitrogen narcosis and the risk of oxygen toxicity.
2. Which gas mixture is most commonly used for deep surface-supplied mixed-gas diving?
Answer: Heliox (helium-oxygen).
3. What is the maximum allowable depth for surface-supplied air diving per ADCI standards?
Answer: 165 fsw (50 msw) in some contexts, but typically limited to 130-165 fsw depending on
operations.
4. What is the primary hazard associated with high partial pressures of oxygen in mixed-gas
diving?
Answer: Central nervous system (CNS) oxygen toxicity.
5. What is the maximum operating depth (MOD) for a helium-oxygen mix with 2% oxygen?
Answer: Calculated using PPO2 = 1.6 ATA (e.g., MOD = (1.6 / FO2) - 33 fsw).
6. According to ADCI, what is the minimum oxygen percentage required in breathing gas for
mixed-gas diving?
Answer: 0.16 ATA (16% at surface).
7. What is the main function of a dive bell in mixed-gas operations?
Answer: To provide a controlled decompression environment and emergency refuge.
, 8. Which regulator is typically used in surface-supplied mixed-gas diving?
Answer: Demand regulator with non-return valve.
9. What is the primary advantage of using helium in breathing mixtures?
Answer: Reduces nitrogen narcosis.
10. What is the recommended maximum PPO2 for mixed-gas diving to avoid CNS toxicity?
Answer: 1.6 ATA.
11. In mixed-gas diving, what is the primary cause of high-pressure nervous syndrome (HPNS)?
Answer: High partial pressure of helium at extreme depths.
12. What is the minimum ventilation rate for helmets/masks in mixed-gas operations?
Answer: 4.5 ft³/min at operating depth.
13. What must be present at the dive site for mixed-gas diving deeper than 130 fsw?
Answer: Decompression chamber.
14. What is the color coding for helium cylinders per ADCI standards?
Answer: Brown with white shoulder.
15. What is the purpose of a non-return valve on the diver's umbilical?
Answer: Prevents loss of gas if umbilical is severed.
16. What is the maximum allowable CO2 in breathing gas?
