South Carolina (SC) LP Gas Dealer & Installer
Practice Exam 200 Questions | PSI LLR Licensing
Test | NFPA 58 & NFPA 54 | Propane Installer
Certification Prep | Updated 2026-2027 | Instant
Pdf Download
Section 1: Propane Properties & LP-Gas Fundamentals (Questions 1–25)
1. LP gas (liquefied petroleum gas) is primarily composed of which of the following?
a) Methane and ethane
b) Propane only
c) Butane and propane
d) Hydrogen and oxygen
LP gas is a mixture of hydrocarbon gases, primarily propane and butane. These gases are
derived from natural gas processing and crude oil refining. Methane is the primary
component of natural gas, not LP gas .
2. What is the boiling point of propane at atmospheric pressure?
a) 32°F (0°C)
b) 0°F (-18°C)
c) -44°F (-42°C)
d) -10°F (-23°C)
*Propane boils at -44°F (-42°C) at atmospheric pressure. This low boiling point means
propane exists as a vapor at most ambient temperatures, which is why it is stored under
pressure to keep it in liquid form. Butane has a higher boiling point (31°F), making it less
suitable for cold climates .*
,3. Which of the following best describes the expansion ratio of propane from liquid to
vapor?
a) 1:50
b) 1:100
c) 1:200
d) 1:270
One gallon of liquid propane expands to approximately 270 gallons of propane vapor at
standard temperature and pressure (60°F). This high expansion ratio explains why liquid
propane leaks are extremely dangerous – a small liquid leak can create a very large volume
of flammable vapor .
4. One gallon of propane contains approximately how many BTUs?
a) 50,000 BTUs
b) 75,000 BTUs
c) 91,500 BTUs
d) 120,000 BTUs
*One gallon of propane contains approximately 91,500 BTUs (British Thermal Units). This is
slightly less than natural gas on a per-gallon equivalent basis but provides consistent
energy content regardless of pipeline pressure variations .*
5. What is the specific gravity of propane vapor (relative to air)?
a) 0.50 (lighter than air)
b) 0.80 (lighter than air)
c) 1.50 (heavier than air)
d) 2.00 (heavier than air)
Propane vapor has a specific gravity of approximately 1.50, meaning it is 1.5 times heavier
than air. This is critical for safety because leaking propane will settle in low areas
(basements, pits, ditches) rather than dissipating upward like natural gas .
,6. What is the specific gravity of liquid propane (relative to water)?
a) 0.50
b) 0.75
c) 1.00
d) 1.25
Liquid propane has a specific gravity of approximately 0.50, meaning it is about half the
weight of water. One gallon of water weighs 8.33 pounds; one gallon of propane weighs
about 4.2 pounds. This affects tank sizing and transport weight calculations .
7. Which odorant is added to propane to aid in leak detection?
a) Sulfur dioxide
b) Ethyl mercaptan
c) Carbon monoxide
d) Methyl chloride
Ethyl mercaptan is added to propane as an odorant to give it a distinctive "rotten egg" smell.
Propane is naturally odorless and colorless. The odorant is added at a ratio of
approximately 1 pound per 10,000 gallons of LP gas to ensure leaks can be detected by
smell .
8. At what temperature does propane freeze?
a) -44°F (propane does not freeze at this temperature; it boils)
b) 32°F
c) -100°F
d) Propane does not freeze under normal conditions; it remains liquid until extremely
cold
*Propane does not freeze under normal atmospheric conditions. It remains a liquid down to
its boiling point (-44°F) but does not solidify until approximately -306°F (-188°C), which is
not encountered in practical applications. This is why propane is used in cold climates
where butane would not vaporize .*
, 9. The ideal combustion ratio for propane is approximately:
a) 1 part propane to 5 parts air
b) 1 part propane to 15 parts air
c) 1 part propane to 24 parts air
d) 1 part propane to 50 parts air
The ideal (stoichiometric) combustion ratio for propane is approximately 1 part propane to
24 parts air (4% propane by volume). Complete combustion produces carbon dioxide and
water vapor. Incomplete combustion (too rich or too lean) produces carbon monoxide, which
is toxic .
10. What is the primary source of LP gases?
a) Coal mining
b) Biomass processing
c) Solar energy conversion
d) Natural gas processing and crude oil refining
LP gases (propane and butane) are byproducts of natural gas processing and crude oil
refining. When natural gas is extracted, heavier hydrocarbons including propane are
removed to prevent pipeline condensation. Similarly, during crude oil refining, propane is
separated from other fractions .
11. Which of the following is an advantage of using propane as a fuel source?
a) Low cost compared to electricity
b) Wide availability in rural areas
c) Clean-burning with low emissions
d) All of the above
*Propane offers multiple advantages: it is often more cost-effective than electricity for
heating, it is available in areas without natural gas pipelines, and it burns cleaner than many
other fossil fuels with lower CO2 and particulate emissions. It is also easily stored in tanks .*
Practice Exam 200 Questions | PSI LLR Licensing
Test | NFPA 58 & NFPA 54 | Propane Installer
Certification Prep | Updated 2026-2027 | Instant
Pdf Download
Section 1: Propane Properties & LP-Gas Fundamentals (Questions 1–25)
1. LP gas (liquefied petroleum gas) is primarily composed of which of the following?
a) Methane and ethane
b) Propane only
c) Butane and propane
d) Hydrogen and oxygen
LP gas is a mixture of hydrocarbon gases, primarily propane and butane. These gases are
derived from natural gas processing and crude oil refining. Methane is the primary
component of natural gas, not LP gas .
2. What is the boiling point of propane at atmospheric pressure?
a) 32°F (0°C)
b) 0°F (-18°C)
c) -44°F (-42°C)
d) -10°F (-23°C)
*Propane boils at -44°F (-42°C) at atmospheric pressure. This low boiling point means
propane exists as a vapor at most ambient temperatures, which is why it is stored under
pressure to keep it in liquid form. Butane has a higher boiling point (31°F), making it less
suitable for cold climates .*
,3. Which of the following best describes the expansion ratio of propane from liquid to
vapor?
a) 1:50
b) 1:100
c) 1:200
d) 1:270
One gallon of liquid propane expands to approximately 270 gallons of propane vapor at
standard temperature and pressure (60°F). This high expansion ratio explains why liquid
propane leaks are extremely dangerous – a small liquid leak can create a very large volume
of flammable vapor .
4. One gallon of propane contains approximately how many BTUs?
a) 50,000 BTUs
b) 75,000 BTUs
c) 91,500 BTUs
d) 120,000 BTUs
*One gallon of propane contains approximately 91,500 BTUs (British Thermal Units). This is
slightly less than natural gas on a per-gallon equivalent basis but provides consistent
energy content regardless of pipeline pressure variations .*
5. What is the specific gravity of propane vapor (relative to air)?
a) 0.50 (lighter than air)
b) 0.80 (lighter than air)
c) 1.50 (heavier than air)
d) 2.00 (heavier than air)
Propane vapor has a specific gravity of approximately 1.50, meaning it is 1.5 times heavier
than air. This is critical for safety because leaking propane will settle in low areas
(basements, pits, ditches) rather than dissipating upward like natural gas .
,6. What is the specific gravity of liquid propane (relative to water)?
a) 0.50
b) 0.75
c) 1.00
d) 1.25
Liquid propane has a specific gravity of approximately 0.50, meaning it is about half the
weight of water. One gallon of water weighs 8.33 pounds; one gallon of propane weighs
about 4.2 pounds. This affects tank sizing and transport weight calculations .
7. Which odorant is added to propane to aid in leak detection?
a) Sulfur dioxide
b) Ethyl mercaptan
c) Carbon monoxide
d) Methyl chloride
Ethyl mercaptan is added to propane as an odorant to give it a distinctive "rotten egg" smell.
Propane is naturally odorless and colorless. The odorant is added at a ratio of
approximately 1 pound per 10,000 gallons of LP gas to ensure leaks can be detected by
smell .
8. At what temperature does propane freeze?
a) -44°F (propane does not freeze at this temperature; it boils)
b) 32°F
c) -100°F
d) Propane does not freeze under normal conditions; it remains liquid until extremely
cold
*Propane does not freeze under normal atmospheric conditions. It remains a liquid down to
its boiling point (-44°F) but does not solidify until approximately -306°F (-188°C), which is
not encountered in practical applications. This is why propane is used in cold climates
where butane would not vaporize .*
, 9. The ideal combustion ratio for propane is approximately:
a) 1 part propane to 5 parts air
b) 1 part propane to 15 parts air
c) 1 part propane to 24 parts air
d) 1 part propane to 50 parts air
The ideal (stoichiometric) combustion ratio for propane is approximately 1 part propane to
24 parts air (4% propane by volume). Complete combustion produces carbon dioxide and
water vapor. Incomplete combustion (too rich or too lean) produces carbon monoxide, which
is toxic .
10. What is the primary source of LP gases?
a) Coal mining
b) Biomass processing
c) Solar energy conversion
d) Natural gas processing and crude oil refining
LP gases (propane and butane) are byproducts of natural gas processing and crude oil
refining. When natural gas is extracted, heavier hydrocarbons including propane are
removed to prevent pipeline condensation. Similarly, during crude oil refining, propane is
separated from other fractions .
11. Which of the following is an advantage of using propane as a fuel source?
a) Low cost compared to electricity
b) Wide availability in rural areas
c) Clean-burning with low emissions
d) All of the above
*Propane offers multiple advantages: it is often more cost-effective than electricity for
heating, it is available in areas without natural gas pipelines, and it burns cleaner than many
other fossil fuels with lower CO2 and particulate emissions. It is also easily stored in tanks .*
