FDNY G-46 EXAM – FIRE DEPARTMENT CITY OF NEW YORK
CERTIFICATE OF FITNESS FOR
HANDLING AND USE OF NON-FLAMMABLE COMPRESSED GASES TEST
PREP (2026/2027) –
200 VERIFIED QUESTIONS & ANSWERS WITH RATIONALES
SECTION 1: DEFINITIONS AND CLASSIFICATIONS (Questions 1–30)
Question 1: According to the FDNY Fire Code, what is the official definition of a
non-flammable gas?
A) A gas that is completely inert and poses no health risks
B) A gas that, at 68°F and 14.7 psia, is not ignitable in a mixture of 13% or less
with air
C) A gas that has a flammable range of more than 12% in air
D) Any gas that is stored below 50 psi
✅ Answer: B – A gas that, at 68°F and 14.7 psia, is not ignitable in a mixture of
13% or less with air
Rationale: The FDNY Fire Code defines a non-flammable gas as one that is NOT
ignitable at 14.7 psia when in a mixture of 13 percent or less by volume with air,
OR does not have a flammable range of at least 12 percent, as determined by
ASTM E681.
Question 2: What is the primary hazard associated with non-flammable
compressed gases?
A) Explosion due to flammability
B) Asphyxiation or oxygen displacement
C) Fire risk from sparks
D) Toxic chemical reactions
✅ Answer: B – Asphyxiation or oxygen displacement
Rationale: Non-flammable gases do not burn, but they displace oxygen in
confined spaces, causing suffocation. Many are odorless/colorless, making
displacement hard to detect.
Question 3: What temperature is used in the FDNY definition of a non-flammable
gas?
A) 32°F
B) 68°F
C) 100°F
1
,D) 125°F
✅ Answer: B – 68°F
Rationale: FDNY specifications for non-flammable gas testing require conditions at
68°F and 14.7 psia.
Question 4: How does FDNY define a "flammable gas" for contrast with non-
flammable?
A) A gas with a flash point below 100°F
B) A gas that is ignitable at 14.7 psia in a mixture of 13% or less with air
C) Any gas stored above 125°F
D) A gas that produces toxic fumes when heated
✅ Answer: B – A gas that is ignitable at 14.7 psia in a mixture of 13% or less with
air
Rationale: A flammable gas is ignitable at 14.7 psia in a mixture of 13% or less by
volume with air, OR has a flammable range of at least 12%, regardless of lower
limit.
Question 5: What is a non-liquefied compressed gas?
A) A gas that is partially liquid at 68°F
B) A gas that is entirely gaseous at 68°F under charged pressure
C) A gas dissolved in a solvent
D) A gas that freezes at room temperature
✅ Answer: B – A gas that is entirely gaseous at 68°F under charged pressure
Rationale: Non-liquefied gases are in packaging under charged pressure and are
entirely gaseous at 68°F (e.g., oxygen, nitrogen, helium).
Question 6: What is a liquefied compressed gas?
A) A gas that remains entirely gaseous at 68°F
B) A gas that is partially liquid at 68°F under charged pressure
C) A gas dissolved in water
D) A gas that turns to liquid below -100°F
✅ Answer: B – A gas that is partially liquid at 68°F under charged pressure
Rationale: Liquefied gases (e.g., carbon dioxide, ammonia, chlorine) exist partially
as liquid at 68°F under pressure.
Question 7: Which of the following is classified as a non-flammable gas under
FDNY G-46?
2
,A) Acetylene
B) Oxygen
C) Ammonia
D) Hydrogen
✅ Answer: C – Ammonia (in the context of DOT non-flammable classification)
Rationale: Ammonia is DOT-classified as non-flammable; however, in high
concentrations (16–25% in air) it can burn, but this is unlikely under normal
handling.
Question 8: What is the classification threshold for a "Highly Toxic Gas" regarding
LC50?
A) LC50 greater than 2000 ppm
B) LC50 between 200 ppm and 2000 ppm
C) LC50 less than or equal to 200 ppm
D) LC50 less than 50 ppm
✅ Answer: C – LC50 less than or equal to 200 ppm
Rationale: A highly toxic gas has an LC50 (lethal concentration, 50% kill rate) of
200 ppm or less when administered for 1 hour.
Question 9: What is the definition of a "Toxic Gas" under FDNY rules?
A) LC50 less than 200 ppm
B) LC50 greater than 200 ppm but not more than 2000 ppm
C) LC50 greater than 5000 ppm
D) Any gas that is a respiratory irritant
✅ Answer: B – LC50 greater than 200 ppm but not more than 2000 ppm
Rationale: Toxic gases have an LC50 between 200 ppm and 2000 ppm per 1-hour
exposure.
Question 10: What does the term "cryogenic fluid" refer to?
A) Any gas stored above 500 psi
B) A gas liquefied at temperatures below -130°F
C) A gas that is radioactive
D) Any gas in a glass container
✅ Answer: B – A gas liquefied at temperatures below -130°F
Rationale: Cryogenic fluids are liquefied gases with boiling points below -130°F
(e.g., liquid nitrogen, liquid helium).
3
, Question 11: Which of the following is considered an oxidizing gas?
A) Nitrogen
B) Helium
C) Oxygen
D) Carbon dioxide
✅ Answer: C – Oxygen
Rationale: Oxygen supports combustion and is classified as an oxidizer, even
though it is non-flammable.
Question 12: Under the FDNY Fire Code, what is the pressure threshold that
defines "high pressure" for gas cylinders?
A) Any pressure above 15 psig
B) Any pressure above 100 psig
C) Any pressure above 200 psig
D) Any pressure above 500 psig
✅ Answer: C – Any pressure above 200 psig (typically 3000–6000 psi for high-
pressure cylinders)
Rationale: High-pressure cylinders generally have service pressures exceeding 200
psig, commonly 2015 to 6000 psig.
Question 13: What does "atmospheric pressure" refer to when discussing gas
storage?
A) 0 psig (14.7 psia)
B) 14.7 psig
C) 0 psia
D) 100 psia
✅ Answer: A – 0 psig (which equals 14.7 psia)
Rationale: Atmospheric pressure at sea level is 14.7 pounds per square inch
absolute (psia), which is 0 pounds per square inch gauge (psig).
Question 14: According to FDNY, a gas is considered "inert" if:
A) It reacts violently with water
B) It does not chemically react under specified conditions and does not support
combustion
C) It has a strong odor
D) It is lighter than air
4
CERTIFICATE OF FITNESS FOR
HANDLING AND USE OF NON-FLAMMABLE COMPRESSED GASES TEST
PREP (2026/2027) –
200 VERIFIED QUESTIONS & ANSWERS WITH RATIONALES
SECTION 1: DEFINITIONS AND CLASSIFICATIONS (Questions 1–30)
Question 1: According to the FDNY Fire Code, what is the official definition of a
non-flammable gas?
A) A gas that is completely inert and poses no health risks
B) A gas that, at 68°F and 14.7 psia, is not ignitable in a mixture of 13% or less
with air
C) A gas that has a flammable range of more than 12% in air
D) Any gas that is stored below 50 psi
✅ Answer: B – A gas that, at 68°F and 14.7 psia, is not ignitable in a mixture of
13% or less with air
Rationale: The FDNY Fire Code defines a non-flammable gas as one that is NOT
ignitable at 14.7 psia when in a mixture of 13 percent or less by volume with air,
OR does not have a flammable range of at least 12 percent, as determined by
ASTM E681.
Question 2: What is the primary hazard associated with non-flammable
compressed gases?
A) Explosion due to flammability
B) Asphyxiation or oxygen displacement
C) Fire risk from sparks
D) Toxic chemical reactions
✅ Answer: B – Asphyxiation or oxygen displacement
Rationale: Non-flammable gases do not burn, but they displace oxygen in
confined spaces, causing suffocation. Many are odorless/colorless, making
displacement hard to detect.
Question 3: What temperature is used in the FDNY definition of a non-flammable
gas?
A) 32°F
B) 68°F
C) 100°F
1
,D) 125°F
✅ Answer: B – 68°F
Rationale: FDNY specifications for non-flammable gas testing require conditions at
68°F and 14.7 psia.
Question 4: How does FDNY define a "flammable gas" for contrast with non-
flammable?
A) A gas with a flash point below 100°F
B) A gas that is ignitable at 14.7 psia in a mixture of 13% or less with air
C) Any gas stored above 125°F
D) A gas that produces toxic fumes when heated
✅ Answer: B – A gas that is ignitable at 14.7 psia in a mixture of 13% or less with
air
Rationale: A flammable gas is ignitable at 14.7 psia in a mixture of 13% or less by
volume with air, OR has a flammable range of at least 12%, regardless of lower
limit.
Question 5: What is a non-liquefied compressed gas?
A) A gas that is partially liquid at 68°F
B) A gas that is entirely gaseous at 68°F under charged pressure
C) A gas dissolved in a solvent
D) A gas that freezes at room temperature
✅ Answer: B – A gas that is entirely gaseous at 68°F under charged pressure
Rationale: Non-liquefied gases are in packaging under charged pressure and are
entirely gaseous at 68°F (e.g., oxygen, nitrogen, helium).
Question 6: What is a liquefied compressed gas?
A) A gas that remains entirely gaseous at 68°F
B) A gas that is partially liquid at 68°F under charged pressure
C) A gas dissolved in water
D) A gas that turns to liquid below -100°F
✅ Answer: B – A gas that is partially liquid at 68°F under charged pressure
Rationale: Liquefied gases (e.g., carbon dioxide, ammonia, chlorine) exist partially
as liquid at 68°F under pressure.
Question 7: Which of the following is classified as a non-flammable gas under
FDNY G-46?
2
,A) Acetylene
B) Oxygen
C) Ammonia
D) Hydrogen
✅ Answer: C – Ammonia (in the context of DOT non-flammable classification)
Rationale: Ammonia is DOT-classified as non-flammable; however, in high
concentrations (16–25% in air) it can burn, but this is unlikely under normal
handling.
Question 8: What is the classification threshold for a "Highly Toxic Gas" regarding
LC50?
A) LC50 greater than 2000 ppm
B) LC50 between 200 ppm and 2000 ppm
C) LC50 less than or equal to 200 ppm
D) LC50 less than 50 ppm
✅ Answer: C – LC50 less than or equal to 200 ppm
Rationale: A highly toxic gas has an LC50 (lethal concentration, 50% kill rate) of
200 ppm or less when administered for 1 hour.
Question 9: What is the definition of a "Toxic Gas" under FDNY rules?
A) LC50 less than 200 ppm
B) LC50 greater than 200 ppm but not more than 2000 ppm
C) LC50 greater than 5000 ppm
D) Any gas that is a respiratory irritant
✅ Answer: B – LC50 greater than 200 ppm but not more than 2000 ppm
Rationale: Toxic gases have an LC50 between 200 ppm and 2000 ppm per 1-hour
exposure.
Question 10: What does the term "cryogenic fluid" refer to?
A) Any gas stored above 500 psi
B) A gas liquefied at temperatures below -130°F
C) A gas that is radioactive
D) Any gas in a glass container
✅ Answer: B – A gas liquefied at temperatures below -130°F
Rationale: Cryogenic fluids are liquefied gases with boiling points below -130°F
(e.g., liquid nitrogen, liquid helium).
3
, Question 11: Which of the following is considered an oxidizing gas?
A) Nitrogen
B) Helium
C) Oxygen
D) Carbon dioxide
✅ Answer: C – Oxygen
Rationale: Oxygen supports combustion and is classified as an oxidizer, even
though it is non-flammable.
Question 12: Under the FDNY Fire Code, what is the pressure threshold that
defines "high pressure" for gas cylinders?
A) Any pressure above 15 psig
B) Any pressure above 100 psig
C) Any pressure above 200 psig
D) Any pressure above 500 psig
✅ Answer: C – Any pressure above 200 psig (typically 3000–6000 psi for high-
pressure cylinders)
Rationale: High-pressure cylinders generally have service pressures exceeding 200
psig, commonly 2015 to 6000 psig.
Question 13: What does "atmospheric pressure" refer to when discussing gas
storage?
A) 0 psig (14.7 psia)
B) 14.7 psig
C) 0 psia
D) 100 psia
✅ Answer: A – 0 psig (which equals 14.7 psia)
Rationale: Atmospheric pressure at sea level is 14.7 pounds per square inch
absolute (psia), which is 0 pounds per square inch gauge (psig).
Question 14: According to FDNY, a gas is considered "inert" if:
A) It reacts violently with water
B) It does not chemically react under specified conditions and does not support
combustion
C) It has a strong odor
D) It is lighter than air
4
