(FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
FDNY G-46
Non-Flammable
Gas – Structured
Questions and
Answers
Compressed Gases
Study Guide for
Compliance and
Exam Preparation
3/16/2026, 6:19:45 PM
,(FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
Definitions & Classifications
Q: What is a non-flammable gas?
A: A gas at 68°F or less at 14.7 psia of pressure which:
● Is NOT ignitable at 14.7 psia when in a mixture of 13% or less by volume with air,
per ASTM E681 testing, OR
● Does NOT have a flammable range at 14.7 psia with air of at least 12%, regardless
of lower limit, per ASTM E681.
Q: Is ammonia nonflammable?
A: Classified by DOT as nonflammable, but ammonia vapor in high concentrations
(16–25% by weight in air) can burn, mostly in confined spaces or near large spills.
Q: What is a flammable gas?
A: A gas at 68°F or less at 14.7 psia which:
1. Is ignitable at 14.7 psia in a mixture of 13% or less by volume with air (ASTM E681),
OR
2. Has a flammable range at 14.7 psia with air of at least 12% (ASTM E681).
Q: What are highly toxic and toxic gases?
A:
● Highly Toxic Gas: LC50 ≤ 200 ppm by volume in air (or ≤ 2 mg/L of mist/fume/dust)
for 1 hr inhalation in albino rats. Example: chlorine.
● Toxic Gas: LC50 200–2000 ppm by volume (or 2–20 mg/L) for 1 hr inhalation.
Q: What is an oxidizing gas?
A: A gas that can support and accelerate combustion of other materials.
3/16/2026, 6:19:45 PM
,(FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
Q: What is a corrosive gas?
A: A gas that causes visible destruction or irreversible chemical alterations to living tissue at
the contact site.
Q: What is a compressed gas?
A: Any gas stored under pressure greater than one atmosphere at 68°F, which may be:
● Nonliquified compressed gas: Entirely gaseous at 68°F.
● Liquified compressed gas: Partially liquid at 68°F.
● Compressed gases in solution: Nonliquified gases dissolved in a solvent.
● Compressed gas mixtures: Two or more gases in one container, hazards
considered collectively.
Q: What is a gas cabinet?
A: A fully enclosed, noncombustible enclosure isolating compressed gas containers during
storage or use, including access doors and control ports.
Permit & Supervision Requirements
Q: Who may handle non-flammable compressed gases in quantities requiring a permit?
A: Only a person holding a G-46 Certificate of Fitness (COF).
Q: What types of permits exist for non-flammable compressed gases?
A:
● Site-specific permit: For a specific location, valid 12 months for permanent, shorter
for temporary. Requires inspection.
● Citywide permit: Allows operations at multiple locations, each location ≤ 30 days.
Exceeding 30 days requires site-specific permit.
3/16/2026, 6:19:45 PM
, (FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
Q: Quantities of gases requiring a permit (SCF)?
A:
● Corrosive – 400 SCF
● Nonflammable/nonoxidizing (except CO2) – 3,000 SCF
● CO2 – 4,500 SCF
● Oxidizing – 504 SCF
● Highly toxic, toxic, unstable/reactive – Any amount
Q: What is personal vs general supervision?
A:
● Personal Supervision: Holder of COF is personally present while duties are
performed.
● General Supervision: COF holder is responsible but need not be on-site at all
times.
Handling & Equipment
Q: What are general handling rules for non-flammable compressed gases?
A:
● Only move, remove, or operate gases as designed.
● Use hoses and regulators appropriately.
● Close container valves before moving cylinders.
● Never mix gases or transfer between containers except by manufacturer/distributor
or COF holder in safe conditions.
Q: What equipment is required for safe operation?
A:
3/16/2026, 6:19:45 PM
FDNY G-46
Non-Flammable
Gas – Structured
Questions and
Answers
Compressed Gases
Study Guide for
Compliance and
Exam Preparation
3/16/2026, 6:19:45 PM
,(FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
Definitions & Classifications
Q: What is a non-flammable gas?
A: A gas at 68°F or less at 14.7 psia of pressure which:
● Is NOT ignitable at 14.7 psia when in a mixture of 13% or less by volume with air,
per ASTM E681 testing, OR
● Does NOT have a flammable range at 14.7 psia with air of at least 12%, regardless
of lower limit, per ASTM E681.
Q: Is ammonia nonflammable?
A: Classified by DOT as nonflammable, but ammonia vapor in high concentrations
(16–25% by weight in air) can burn, mostly in confined spaces or near large spills.
Q: What is a flammable gas?
A: A gas at 68°F or less at 14.7 psia which:
1. Is ignitable at 14.7 psia in a mixture of 13% or less by volume with air (ASTM E681),
OR
2. Has a flammable range at 14.7 psia with air of at least 12% (ASTM E681).
Q: What are highly toxic and toxic gases?
A:
● Highly Toxic Gas: LC50 ≤ 200 ppm by volume in air (or ≤ 2 mg/L of mist/fume/dust)
for 1 hr inhalation in albino rats. Example: chlorine.
● Toxic Gas: LC50 200–2000 ppm by volume (or 2–20 mg/L) for 1 hr inhalation.
Q: What is an oxidizing gas?
A: A gas that can support and accelerate combustion of other materials.
3/16/2026, 6:19:45 PM
,(FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
Q: What is a corrosive gas?
A: A gas that causes visible destruction or irreversible chemical alterations to living tissue at
the contact site.
Q: What is a compressed gas?
A: Any gas stored under pressure greater than one atmosphere at 68°F, which may be:
● Nonliquified compressed gas: Entirely gaseous at 68°F.
● Liquified compressed gas: Partially liquid at 68°F.
● Compressed gases in solution: Nonliquified gases dissolved in a solvent.
● Compressed gas mixtures: Two or more gases in one container, hazards
considered collectively.
Q: What is a gas cabinet?
A: A fully enclosed, noncombustible enclosure isolating compressed gas containers during
storage or use, including access doors and control ports.
Permit & Supervision Requirements
Q: Who may handle non-flammable compressed gases in quantities requiring a permit?
A: Only a person holding a G-46 Certificate of Fitness (COF).
Q: What types of permits exist for non-flammable compressed gases?
A:
● Site-specific permit: For a specific location, valid 12 months for permanent, shorter
for temporary. Requires inspection.
● Citywide permit: Allows operations at multiple locations, each location ≤ 30 days.
Exceeding 30 days requires site-specific permit.
3/16/2026, 6:19:45 PM
, (FDNY G-46 Non-Flammable Gas – Structured Questions and Answers Compressed Gases Study Guide for Compliance and Exam Preparation 2026)
Q: Quantities of gases requiring a permit (SCF)?
A:
● Corrosive – 400 SCF
● Nonflammable/nonoxidizing (except CO2) – 3,000 SCF
● CO2 – 4,500 SCF
● Oxidizing – 504 SCF
● Highly toxic, toxic, unstable/reactive – Any amount
Q: What is personal vs general supervision?
A:
● Personal Supervision: Holder of COF is personally present while duties are
performed.
● General Supervision: COF holder is responsible but need not be on-site at all
times.
Handling & Equipment
Q: What are general handling rules for non-flammable compressed gases?
A:
● Only move, remove, or operate gases as designed.
● Use hoses and regulators appropriately.
● Close container valves before moving cylinders.
● Never mix gases or transfer between containers except by manufacturer/distributor
or COF holder in safe conditions.
Q: What equipment is required for safe operation?
A:
3/16/2026, 6:19:45 PM
