CETP 1.0 Module 5 EXAM 100% Verified Questions and Answers 2025
Question 1
The following ingredient is needed to start and sustain combustion:
A) Oxygen
B) Carbon Monoxide
C) Gasoline
D) Odorant
E) Water Vapor
Correct Answer: A) Oxygen
Rationale: Combustion, also known as burning, is a chemical process that requires three
essential components, often referred to as the "fire triangle": fuel, heat (to reach ignition
temperature), and an oxidizer. For propane and most common fuels, oxygen from the air
acts as the oxidizer, making it crucial for both initiating and sustaining the combustion
reaction.
Question 2
The ideal gas-air mixture for propane is approximately _____.
A) 24 parts of propane to 1 part of air
B) 1 part of propane to 24 parts of air
C) 96 parts of propane to 4 parts of air
D) 2.15 parts of propane to 9.60 parts of air
E) 1 part of propane to 15 parts of air
Correct Answer: B) 1 part of propane to 24 parts of air
Rationale: For efficient and complete combustion, propane requires a significant amount of
air (and thus oxygen). The ideal (stoichiometric) mixture for propane combustion is
approximately 1 part propane vapor to 23.8 parts of air, often rounded to 1 part propane to
24 parts of air. This ratio ensures that there is enough oxygen to completely oxidize the
propane, producing primarily carbon dioxide and water vapor.
Question 3
The minimum ignition temperature of propane is approximately _____.
A) 920°F (493°C)
B) 2000°F (1093°C)
C) 720°F (382°C)
D) 1150°F (621°C)
E) 450°F (232°C)
Correct Answer: A) 920°F (493°C)
Rationale: The minimum ignition temperature is the lowest temperature at which a
substance will spontaneously ignite in a normal atmosphere without an external ignition
source. For propane, this temperature is approximately 920°F (493°C). It's important to
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note that a spark or flame can ignite propane at lower temperatures if the gas-air mixture
is within its flammable limits.
Question 4
According to reference information in the NFPA 58 LP-Gas Code, the heat value of propane
vapor is 1,488 BTU per cubic foot of gas.
A) True
B) False
C) This value varies significantly based on atmospheric pressure.
D) This value refers to liquid propane, not vapor.
E) The correct value is 2,516 BTU/cubic foot.
Correct Answer: B) False
Rationale: The heat value of propane vapor is approximately 2,516 BTU per cubic foot of
gas. The value of 1,488 BTU per cubic foot is typically associated with natural gas, not
propane vapor. NFPA 58 contains detailed information on LP-Gas properties, and
understanding these values is crucial for proper system design and safety calculations.
Question 5
Products of complete combustion of propane include water vapor and _____.
A) Carbon Monoxide
B) Carbon Dioxide
C) Aldehydes
D) Soot
E) Sulfur Dioxide
Correct Answer: B) Carbon Dioxide
Rationale: Complete combustion occurs when a fuel (like propane) burns in the presence of
an adequate supply of oxygen. The primary products of complete combustion of
hydrocarbons are carbon dioxide (CO2) and water vapor (H2O). Incomplete combustion,
on the other hand, produces more harmful byproducts.
Question 6
An odorless, highly toxic product of incomplete combustion is _____.
A) Ethyl Mercaptan
B) Water Vapor
C) Carbon Dioxide
D) Carbon Monoxide
E) Nitrogen Oxides
Correct Answer: D) Carbon Monoxide
Rationale: Carbon monoxide (CO) is a dangerous byproduct of incomplete combustion. It is
highly toxic because it binds to hemoglobin in red blood cells much more readily than
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oxygen, thereby reducing the blood's oxygen-carrying capacity. Critically, CO is colorless
and odorless, making it undetectable by human senses without a CO detector, thus posing a
significant threat.
Question 7
_____ is a product of incomplete combustion that is toxic and gives off a strong odor?
A) Soot
B) Aldehydes
C) Ethyl Mercaptan
D) Oxygen
E) Methane
Correct Answer: B) Aldehydes
Rationale: Aldehydes are a group of organic compounds that can be produced during
incomplete combustion, particularly when there is insufficient oxygen. They are toxic and
are known for having strong, pungent, and irritating odors, which can serve as a warning
sign of incomplete combustion conditions. Soot is also a product of incomplete combustion
but does not necessarily have a strong odor; ethyl mercaptan is an added odorant to
propane, not a combustion product.
Question 8
If the odor of aldehydes is present, then carbon monoxide is almost definitely present.
A) True
B) False
C) Aldehydes and carbon monoxide are never present together.
D) Aldehydes only indicate the presence of soot.
E) Only a carbon monoxide detector can confirm the presence of carbon monoxide.
Correct Answer: A) True
Rationale: Both aldehydes and carbon monoxide are products of incomplete combustion.
Therefore, the presence of the distinct, pungent odor of aldehydes is a strong indicator that
combustion is incomplete, and as a result, carbon monoxide is very likely being produced.
This makes the odor of aldehydes an important warning sign.
Question 9
The lower flammability limit (LFL) of propane vapor in a gas-air mixture is _____.
A) 9.60%
B) 5.88%
C) 2.15%
D) 11.70%
E) 15.00%
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Correct Answer: C) 2.15%
Rationale: The lower flammability limit (LFL) for propane indicates the minimum
concentration of propane vapor in air (by volume) required for the mixture to be ignitable.
Below this concentration, the mixture is too "lean" (not enough fuel) to burn. For propane,
the LFL is approximately 2.15%.
Question 10
The upper flammability limit (UFL) of propane vapor in a gas-air mixture is _____.
A) 9.60%
B) 5.88%
C) 2.15%
D) 11.70%
E) 15.00%
Correct Answer: A) 9.60%
Rationale: The upper flammability limit (UFL) for propane indicates the maximum
concentration of propane vapor in air (by volume) above which the mixture is too "rich"
(too much fuel, not enough oxygen) to burn. For propane, the UFL is approximately 9.60%.
Any concentration between the LFL (2.15%) and UFL (9.60%) is considered flammable.
Question 11
The ignition source needed to cause combustion must provide enough _____ to the mixture of
fuel and oxygen to raise the propane to its ignition temperature?
A) Water Vapor
B) Fuel
C) Heat
D) Chemicals
E) Pressure
Correct Answer: C) Heat
Rationale: For combustion to occur, a mixture of fuel and oxygen must be brought to its
ignition temperature. The ignition source provides the necessary heat energy to initiate the
chemical reaction. This heat can come from a spark, flame, hot surface, or electrical arc.
Question 12
Air is made of about 20% oxygen.
A) True
B) False
C) Air is primarily composed of carbon dioxide.
D) Air is about 50% oxygen.
E) Air is 100% oxygen.
Question 1
The following ingredient is needed to start and sustain combustion:
A) Oxygen
B) Carbon Monoxide
C) Gasoline
D) Odorant
E) Water Vapor
Correct Answer: A) Oxygen
Rationale: Combustion, also known as burning, is a chemical process that requires three
essential components, often referred to as the "fire triangle": fuel, heat (to reach ignition
temperature), and an oxidizer. For propane and most common fuels, oxygen from the air
acts as the oxidizer, making it crucial for both initiating and sustaining the combustion
reaction.
Question 2
The ideal gas-air mixture for propane is approximately _____.
A) 24 parts of propane to 1 part of air
B) 1 part of propane to 24 parts of air
C) 96 parts of propane to 4 parts of air
D) 2.15 parts of propane to 9.60 parts of air
E) 1 part of propane to 15 parts of air
Correct Answer: B) 1 part of propane to 24 parts of air
Rationale: For efficient and complete combustion, propane requires a significant amount of
air (and thus oxygen). The ideal (stoichiometric) mixture for propane combustion is
approximately 1 part propane vapor to 23.8 parts of air, often rounded to 1 part propane to
24 parts of air. This ratio ensures that there is enough oxygen to completely oxidize the
propane, producing primarily carbon dioxide and water vapor.
Question 3
The minimum ignition temperature of propane is approximately _____.
A) 920°F (493°C)
B) 2000°F (1093°C)
C) 720°F (382°C)
D) 1150°F (621°C)
E) 450°F (232°C)
Correct Answer: A) 920°F (493°C)
Rationale: The minimum ignition temperature is the lowest temperature at which a
substance will spontaneously ignite in a normal atmosphere without an external ignition
source. For propane, this temperature is approximately 920°F (493°C). It's important to
,[Type here]
note that a spark or flame can ignite propane at lower temperatures if the gas-air mixture
is within its flammable limits.
Question 4
According to reference information in the NFPA 58 LP-Gas Code, the heat value of propane
vapor is 1,488 BTU per cubic foot of gas.
A) True
B) False
C) This value varies significantly based on atmospheric pressure.
D) This value refers to liquid propane, not vapor.
E) The correct value is 2,516 BTU/cubic foot.
Correct Answer: B) False
Rationale: The heat value of propane vapor is approximately 2,516 BTU per cubic foot of
gas. The value of 1,488 BTU per cubic foot is typically associated with natural gas, not
propane vapor. NFPA 58 contains detailed information on LP-Gas properties, and
understanding these values is crucial for proper system design and safety calculations.
Question 5
Products of complete combustion of propane include water vapor and _____.
A) Carbon Monoxide
B) Carbon Dioxide
C) Aldehydes
D) Soot
E) Sulfur Dioxide
Correct Answer: B) Carbon Dioxide
Rationale: Complete combustion occurs when a fuel (like propane) burns in the presence of
an adequate supply of oxygen. The primary products of complete combustion of
hydrocarbons are carbon dioxide (CO2) and water vapor (H2O). Incomplete combustion,
on the other hand, produces more harmful byproducts.
Question 6
An odorless, highly toxic product of incomplete combustion is _____.
A) Ethyl Mercaptan
B) Water Vapor
C) Carbon Dioxide
D) Carbon Monoxide
E) Nitrogen Oxides
Correct Answer: D) Carbon Monoxide
Rationale: Carbon monoxide (CO) is a dangerous byproduct of incomplete combustion. It is
highly toxic because it binds to hemoglobin in red blood cells much more readily than
,[Type here]
oxygen, thereby reducing the blood's oxygen-carrying capacity. Critically, CO is colorless
and odorless, making it undetectable by human senses without a CO detector, thus posing a
significant threat.
Question 7
_____ is a product of incomplete combustion that is toxic and gives off a strong odor?
A) Soot
B) Aldehydes
C) Ethyl Mercaptan
D) Oxygen
E) Methane
Correct Answer: B) Aldehydes
Rationale: Aldehydes are a group of organic compounds that can be produced during
incomplete combustion, particularly when there is insufficient oxygen. They are toxic and
are known for having strong, pungent, and irritating odors, which can serve as a warning
sign of incomplete combustion conditions. Soot is also a product of incomplete combustion
but does not necessarily have a strong odor; ethyl mercaptan is an added odorant to
propane, not a combustion product.
Question 8
If the odor of aldehydes is present, then carbon monoxide is almost definitely present.
A) True
B) False
C) Aldehydes and carbon monoxide are never present together.
D) Aldehydes only indicate the presence of soot.
E) Only a carbon monoxide detector can confirm the presence of carbon monoxide.
Correct Answer: A) True
Rationale: Both aldehydes and carbon monoxide are products of incomplete combustion.
Therefore, the presence of the distinct, pungent odor of aldehydes is a strong indicator that
combustion is incomplete, and as a result, carbon monoxide is very likely being produced.
This makes the odor of aldehydes an important warning sign.
Question 9
The lower flammability limit (LFL) of propane vapor in a gas-air mixture is _____.
A) 9.60%
B) 5.88%
C) 2.15%
D) 11.70%
E) 15.00%
, [Type here]
Correct Answer: C) 2.15%
Rationale: The lower flammability limit (LFL) for propane indicates the minimum
concentration of propane vapor in air (by volume) required for the mixture to be ignitable.
Below this concentration, the mixture is too "lean" (not enough fuel) to burn. For propane,
the LFL is approximately 2.15%.
Question 10
The upper flammability limit (UFL) of propane vapor in a gas-air mixture is _____.
A) 9.60%
B) 5.88%
C) 2.15%
D) 11.70%
E) 15.00%
Correct Answer: A) 9.60%
Rationale: The upper flammability limit (UFL) for propane indicates the maximum
concentration of propane vapor in air (by volume) above which the mixture is too "rich"
(too much fuel, not enough oxygen) to burn. For propane, the UFL is approximately 9.60%.
Any concentration between the LFL (2.15%) and UFL (9.60%) is considered flammable.
Question 11
The ignition source needed to cause combustion must provide enough _____ to the mixture of
fuel and oxygen to raise the propane to its ignition temperature?
A) Water Vapor
B) Fuel
C) Heat
D) Chemicals
E) Pressure
Correct Answer: C) Heat
Rationale: For combustion to occur, a mixture of fuel and oxygen must be brought to its
ignition temperature. The ignition source provides the necessary heat energy to initiate the
chemical reaction. This heat can come from a spark, flame, hot surface, or electrical arc.
Question 12
Air is made of about 20% oxygen.
A) True
B) False
C) Air is primarily composed of carbon dioxide.
D) Air is about 50% oxygen.
E) Air is 100% oxygen.
