Test your Enriched Air Knowledge
Understanding Enriched Air Nitrox
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You may have read Divetalking articles on the subject on Understanding Nitrox or are about to. Perhaps you are looking at getting certified. What ever the reasons, you are here to challenge your knowledge on subjects related to Nitrox. You will be asked a question and posed with a series of answers. Select the best answer to the question. Your score will be tallied allowing you to look further into the ones you missed or a deserving pat on the back for scoring 100%. Questions are asked in the order which allow them to build upon the previous question. If you answer questions correctly, following questions should be easier to answer. Good Luck
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Question 1 of 24
1. Question
1 pointsWhy get nitrox certified
Correct
Correct. One of the benefits is extended bottom time. You may hear it as extended No Decompression Limit, NDL
Incorrect
Hmm… Is that the Best Answer?

Question 2 of 24
2. Question
1 pointsWhat is Nitrox?
Correct
Correct
Incorrect
There may be a better answer

Question 3 of 24
3. Question
1 pointsIf your Nitrox cylinder is filled with 32% Oxygen, what percentage of Nitrogen is in the cylinder?
Correct
Correct
Incorrect
Got a calculator?
Hint
100 minus 32 (100 – 32) = ??

Question 4 of 24
4. Question
1 pointsWhile a new diver may not be good with their gas management, what reason would a new diver earn a Nitrox Certification?
Correct
Correct. Reduced Nitrogen accumulation in the body is one of the benefits of diving Nitrox.
Incorrect
I think there may be a better answer
Hint
One benefit for diving Nitrox is extended bottom time. Another benefit has to do with the reduction of Nitrogen in the cylinder

Question 5 of 24
5. Question
1 pointsHow many Pounds per square inch, psi are exerted on your body at sea level?
Correct
Correct
Incorrect
1 atmosphere, (1atm) from sea level up into space is approx 14.7psi. It is the weight of air pushing down on our body.

Question 6 of 24
6. Question
1 pointsWhat is the difference in ATM and ATA?
Correct
Correct. ata is the addition of the 1 atm of air pressing down on the surface at sea level. Basically atm+1
Incorrect
The second ‘a’ in ata stands for Absolute. It represents the addition of the 1 atm of air pressing o the surface of the ocean. Without that pressure being represented, your would write atm. Add the 1 atm of air you get ata.
ATA=atm+1 
Question 7 of 24
7. Question
1 pointsHow many Atmospheres of sea water are above you when are you in 66 feet sea water?
Correct
Correct
Incorrect
You didn’t add the atmosphere of air did you?
Hint
ATM=(Depth/33)

Question 8 of 24
8. Question
1 pointsHow many Atmospheres Absolute are you at when at 99fsw?
Correct
Correct
Incorrect
Did you forget to add the 1atm of air?
Hint
ATA=((Depth / 33 ) + 1)

Question 9 of 24
9. Question
1 pointsHow many ATA are you at when you are at 87fsw?
Correct
Correct
Incorrect
Forget that 1 atm of air?
Hint
ATA=(( Depth / 33 ) + 1)

Question 10 of 24
10. Question
1 pointsYour Nitrox cylinder is filled with 30% Oxygen. What is the PPO at 66fsw?
Correct
Correct
Incorrect
PPO is a multiple of the percent times the Atmospheres Absolute
Hint
PPO is a multiple of the percent times the Atmospheres Absolute

Question 11 of 24
11. Question
1 pointsYour cylinder is filled with 32% Oxygen and you are at a depth of 97fsw. What is your PPO?
Correct
Correct
Incorrect
Please check your math
Hint
PPO=(( Depth / 33 ) + 1) * .32

Question 12 of 24
12. Question
1 pointsWhat is your Oxygen Equivalent at 80 feet on a cylinder filled with 28% Oxygen?
Correct
Correct
Incorrect
Check hints…
Hint
Oxygen Equivalent=(( Depth / 33 ) + 1 ) * FO

Question 13 of 24
13. Question
1 pointsWhat is the Maximum Operating Depth on EAN32?
Correct
Correct
Incorrect
Maximum Operating Depth, MOD=(PPO / FO) – 1) * 33
Hint
MOD=(PPO / FO) – 1) * 33
The dive industry promotes dive to depth that allows no more than a PPO of 1.4 
Question 14 of 24
14. Question
1 pointsYou are at a depth of 66fsw. You are breathing the equivalent of 96% Oxygen. What is the PPO at this depth?
Correct
Correct
Incorrect
PPO at depth is equal to the Equivalent Percent of Oxygen at depth. It is the product of (FO * ATA)
Hint
PPO=((( Depth / 33 ) + 1 ) * FO)
FO=(PPO / (( Depth / 33 ) + 1 )) 
Question 15 of 24
15. Question
1 pointsWhat is meant by Oxygen Exposure?
Correct
Correct
Incorrect
Accumulative time represented as a percentage of Oxygen Exposure on the body on a PPO greater than .21

Question 16 of 24
16. Question
1 pointsWhat are some of the symptoms of extensive exposure to high levels of Oxygen over time?
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Correct
Incorrect
Symptoms which a physiological and may be felt, seen or heard. They usually come on without warning and could cause harm or death.
Hint
Tinea
Nausia
Dizzyness
Humming or sensation of vibrations 
Question 17 of 24
17. Question
1 pointsThe higher the percent Oxygen in your cylinder is, the deeper you may dive.
Correct
Correct
Incorrect
The deeper you go the higher the PPO and a PPO of 1.4 should not be exceeded. The opposite is true. The higher the percent Oxygen in the cylinder, the Shallower one must dive.
Hint
Do not exceed a PPO of 1.4. Your PPO dictates your MOD and that is influenced by the FO in the cylinder. The higher the FO, the shallower one must dive.

Question 18 of 24
18. Question
1 pointsSelect the best answer: As you descend the water column,
Correct
Correct
Incorrect
Does the gas you are carrying last longer or shorter at depth?
Hint

Question 19 of 24
19. Question
1 pointsWhat is the main reason you analyze your scuba cylinder after being filled?
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Correct
Incorrect
Yes, to learn the FO and what do you do with that knowledge
Hint
MOD=((PPO / FO) – 1) * 33

Question 20 of 24
20. Question
1 pointsWhat is MOD?
Correct
Correct
Incorrect
Maximum Operating Depth
Hint
MOD=((PPO/FO) – 1) * 33

Question 21 of 24
21. Question
1 pointsWhich is the correct formula to calculate MOD?
Correct
Correct…
Incorrect
I sure hope hope your answer resulted in a depth less than MOD
Hint
MOD=Take the max PPO, divide by the FO. Subtract 1 and then multiply that by the depth of 1atm of sea water.

Question 22 of 24
22. Question
1 pointsOn the subject of Equivalent Air Depth, EAD What is your EAD on a 36% mix at 76fsw?
Correct
Correct
Incorrect
Hint
Locate the next deepest depth, 80fsw in this case, look to the right under the EAD column and you find 59fsw. 
Question 23 of 24
23. Question
1 pointsYou perform a series of dives on Nitrox. Your first dive was a PPO=1.28 for 46 minutes and the second dive to a PPO=.94 for 51 minutes.
What is your accumulated Oxygen Exposure after the second dive?
Correct
Correct
Incorrect
Remember to round up and add the two percentages from both dives togetherHint
After the first dive your Percent Allowable Exposure is 30%. You come to this value by taking the PPO=1.28 and rounding it to 1.3, take the 46 minutes and use the next highest time of 54 minutes and scan to the right to find 30% after the first dive.
Calculate the second dive and add that to the first dive and you get? 
Question 24 of 24
24. Question
1 pointsWhat is the Maximum Oxygen Exposure recommended you not exceed in a day?
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Correct
Incorrect
Hint