, CETP Pre-Certification
Review Exam Questions and
Answers with Rationale
Latest Updated 2026/2027
Domain 1: Basic Principles and Propane
Characteristics
Q1. What is the approximate specific gravity
of propane vapor compared to air?
A) 0.50
B) 1.00
C) 1.50
D) 2.00
Correct Answer: C
Rationale: Propane vapor is about 1.5 times
heavier than air. (Specific gravity of air is
1.00). This means propane vapor will tend to
settle in low-lying areas, such as basements
or ditches, if a leak occurs.
,Q2. Why is an odorant added to propane,
and what is the most common odorant used?
A) To make propane burn hotter; Ethyl
Mercaptan.
B) To detect leaks; Ethyl Mercaptan.
C) To make propane more stable; Butane.
D) To change propane from a liquid to a
gas; Methane.
Correct Answer: B
Rationale: Propane is naturally odorless. A
distinct odorant, typically Ethyl Mercaptan,
is added so that leaks can be detected by
smell before they reach dangerous
concentrations.
Q3. At what percentage concentration in air
does propane vapor reach its Lower
Flammable Limit (LFL)?
A) 1.0%
B) 2.15%
C) 9.60%
D) 15.0%
, Correct Answer: B
Rationale: Propane’s flammable range is
relatively narrow. The LFL is 2.15%, and
the Upper Flammable Limit (UFL) is 9.60%.
Any concentration within this range can
ignite if an ignition source is present.
Q4. How does temperature affect the
pressure of liquid propane inside a storage
container?
A) Pressure decreases as temperature
increases.
B) Pressure remains constant regardless of
temperature.
C) Pressure increases significantly as
temperature increases.
D) Temperature only affects the odorant, not
the pressure.
Correct Answer: C
Rationale: Like most liquids, propane
expands when heated. Because it is stored in
a confined container, this expansion causes a
corresponding rise in vapor pressure. This
Review Exam Questions and
Answers with Rationale
Latest Updated 2026/2027
Domain 1: Basic Principles and Propane
Characteristics
Q1. What is the approximate specific gravity
of propane vapor compared to air?
A) 0.50
B) 1.00
C) 1.50
D) 2.00
Correct Answer: C
Rationale: Propane vapor is about 1.5 times
heavier than air. (Specific gravity of air is
1.00). This means propane vapor will tend to
settle in low-lying areas, such as basements
or ditches, if a leak occurs.
,Q2. Why is an odorant added to propane,
and what is the most common odorant used?
A) To make propane burn hotter; Ethyl
Mercaptan.
B) To detect leaks; Ethyl Mercaptan.
C) To make propane more stable; Butane.
D) To change propane from a liquid to a
gas; Methane.
Correct Answer: B
Rationale: Propane is naturally odorless. A
distinct odorant, typically Ethyl Mercaptan,
is added so that leaks can be detected by
smell before they reach dangerous
concentrations.
Q3. At what percentage concentration in air
does propane vapor reach its Lower
Flammable Limit (LFL)?
A) 1.0%
B) 2.15%
C) 9.60%
D) 15.0%
, Correct Answer: B
Rationale: Propane’s flammable range is
relatively narrow. The LFL is 2.15%, and
the Upper Flammable Limit (UFL) is 9.60%.
Any concentration within this range can
ignite if an ignition source is present.
Q4. How does temperature affect the
pressure of liquid propane inside a storage
container?
A) Pressure decreases as temperature
increases.
B) Pressure remains constant regardless of
temperature.
C) Pressure increases significantly as
temperature increases.
D) Temperature only affects the odorant, not
the pressure.
Correct Answer: C
Rationale: Like most liquids, propane
expands when heated. Because it is stored in
a confined container, this expansion causes a
corresponding rise in vapor pressure. This
