PADI Enriched Air (Nitrox) Diver Exam – 400
Practice Questions with Verified Answers &
Detailed Rationales (2026 Updated)
Section 1: Enriched Air Fundamentals
Question 1
What is the primary benefit of diving with enriched air (EANx) compared to
standard air?
• A) It allows divers to breathe at greater depths without risk of nitrogen
narcosis
• B) It extends no-decompression limits by reducing nitrogen absorption at a
given depth
• C) It eliminates the need for decompression stops on all dives
• D) It increases the density of the breathing gas, reducing breathing effort
Correct Answer: B) It extends no-decompression limits by reducing nitrogen
absorption at a given depth
Rationale: Enriched air contains a higher percentage of oxygen and a lower
percentage of nitrogen than standard air (21% O₂). The reduced nitrogen partial
pressure at a given depth means less nitrogen is absorbed, which extends no-
decompression limits. It does not eliminate all decompression requirements, nor
does it address nitrogen narcosis at extreme depths .
Question 2
What is "enriched air" as defined in PADI materials?
• A) Air that has been compressed to a higher pressure
, • B) Any nitrogen/oxygen gas blend with more than 21% oxygen
• C) Air that has been filtered to remove all contaminants
• D) Pure oxygen used for decompression stops
Correct Answer: B) Any nitrogen/oxygen gas blend with more than 21% oxygen
Rationale: Enriched air is defined as any nitrogen/oxygen gas blend with more
than 21% oxygen. The most common blends are EANx32 and EANx36. The term
"Nitrox" is commonly used to describe enriched air mixtures .
Question 3
What does "EANx36" stand for?
• A) Enriched Air Nitrogen 36% nitrogen
• B) Enriched Air Nitrox 36% oxygen
• C) Extreme Air Nitrox 36% oxygen
• D) Enhanced Air Nitrogen 36% oxygen
Correct Answer: B) Enriched Air Nitrox 36% oxygen
Rationale: In PADI notation, EANx36 indicates enriched air nitrox with 36%
oxygen. The "x" is a placeholder for the specific oxygen percentage. The balance
gas (64%) is primarily nitrogen .
Question 4
For recreational enriched air diving, what is the maximum oxygen percentage
typically used?
• A) 32%
• B) 36%
• C) 40%
• D) 50%
Correct Answer: C) 40%
, Rationale: PADI recreational enriched air training covers blends up to 40% oxygen.
While some technical diving uses higher percentages, the standard recreational
limit is 40% O₂ due to oxygen toxicity concerns and equipment compatibility
requirements .
Question 5
What are the two most common blends of enriched air?
• A) EANx21 and EANx28
• B) EANx32 and EANx36
• C) EANx40 and EANx50
• D) EANx22 and EANx25
Correct Answer: B) EANx32 and EANx36
Rationale: The two most commonly used blends are EANx32 (32% oxygen) and
EANx36 (36% oxygen). EANx32 is also referred to as "Nitrox 32" and EANx36 as
"Nitrox 36" .
Question 6
When diving with enriched air nitrox, for a given depth you should expect narcosis
to be ______ compared to diving with air.
• A) Significantly less
• B) Significantly more
• C) The same as
• D) Eliminated entirely
Correct Answer: C) The same as
Rationale: Although enriched air has less nitrogen than air, oxygen has been
shown to be about as narcotic as nitrogen. Therefore, the current thinking is that
the narcosis potential is the same when diving with enriched air compared to air
at the same depth .
Practice Questions with Verified Answers &
Detailed Rationales (2026 Updated)
Section 1: Enriched Air Fundamentals
Question 1
What is the primary benefit of diving with enriched air (EANx) compared to
standard air?
• A) It allows divers to breathe at greater depths without risk of nitrogen
narcosis
• B) It extends no-decompression limits by reducing nitrogen absorption at a
given depth
• C) It eliminates the need for decompression stops on all dives
• D) It increases the density of the breathing gas, reducing breathing effort
Correct Answer: B) It extends no-decompression limits by reducing nitrogen
absorption at a given depth
Rationale: Enriched air contains a higher percentage of oxygen and a lower
percentage of nitrogen than standard air (21% O₂). The reduced nitrogen partial
pressure at a given depth means less nitrogen is absorbed, which extends no-
decompression limits. It does not eliminate all decompression requirements, nor
does it address nitrogen narcosis at extreme depths .
Question 2
What is "enriched air" as defined in PADI materials?
• A) Air that has been compressed to a higher pressure
, • B) Any nitrogen/oxygen gas blend with more than 21% oxygen
• C) Air that has been filtered to remove all contaminants
• D) Pure oxygen used for decompression stops
Correct Answer: B) Any nitrogen/oxygen gas blend with more than 21% oxygen
Rationale: Enriched air is defined as any nitrogen/oxygen gas blend with more
than 21% oxygen. The most common blends are EANx32 and EANx36. The term
"Nitrox" is commonly used to describe enriched air mixtures .
Question 3
What does "EANx36" stand for?
• A) Enriched Air Nitrogen 36% nitrogen
• B) Enriched Air Nitrox 36% oxygen
• C) Extreme Air Nitrox 36% oxygen
• D) Enhanced Air Nitrogen 36% oxygen
Correct Answer: B) Enriched Air Nitrox 36% oxygen
Rationale: In PADI notation, EANx36 indicates enriched air nitrox with 36%
oxygen. The "x" is a placeholder for the specific oxygen percentage. The balance
gas (64%) is primarily nitrogen .
Question 4
For recreational enriched air diving, what is the maximum oxygen percentage
typically used?
• A) 32%
• B) 36%
• C) 40%
• D) 50%
Correct Answer: C) 40%
, Rationale: PADI recreational enriched air training covers blends up to 40% oxygen.
While some technical diving uses higher percentages, the standard recreational
limit is 40% O₂ due to oxygen toxicity concerns and equipment compatibility
requirements .
Question 5
What are the two most common blends of enriched air?
• A) EANx21 and EANx28
• B) EANx32 and EANx36
• C) EANx40 and EANx50
• D) EANx22 and EANx25
Correct Answer: B) EANx32 and EANx36
Rationale: The two most commonly used blends are EANx32 (32% oxygen) and
EANx36 (36% oxygen). EANx32 is also referred to as "Nitrox 32" and EANx36 as
"Nitrox 36" .
Question 6
When diving with enriched air nitrox, for a given depth you should expect narcosis
to be ______ compared to diving with air.
• A) Significantly less
• B) Significantly more
• C) The same as
• D) Eliminated entirely
Correct Answer: C) The same as
Rationale: Although enriched air has less nitrogen than air, oxygen has been
shown to be about as narcotic as nitrogen. Therefore, the current thinking is that
the narcosis potential is the same when diving with enriched air compared to air
at the same depth .
