Page 1 of 95
New Mexico (NM) LP‑9 Station for Dispensing LP‑Gas
Exam Actual Test Questions and Correct Answers With
Rationales LATEST THIS YEAR
EXAM COVERAGE (Point Form)
• LP-Gas Properties & Hazards: Chemical formula (C₃H₈), boiling point (–44°F), vapor pressure
(exponential with temp), specific gravity (liquid 0.5, vapor 1.5–2.0), flammability limits (2.1%–
9.5%), auto-ignition (530°F), odorant (ethyl mercaptan) .
• Container Construction & Identification: ASME vs. DOT specifications, water capacity stamps,
tare weight (TW), requalification dates (5-year visual, 12-year hydrostatic), OPD valves .
• Fill Limits & Gauging: 80% fill rule (liquid expansion), fixed liquid level gauge (spit valve/spitter),
bleeder valves, prevention of overfilling .
• Dispensing Equipment & Operation: Transfer hoses (rated min 350 psig), emergency shear
valves, excess-flow valves, bypass valves, breakaway devices, pump operation .
• NMAC & NFPA 58 Requirements: Self-service dispenser rules (ASME containers only, no DOT
cylinders), emergency shutdown devices, posted instructions, breakaway devices, annual QP
card renewal .
• Transportation & Vehicle Loading: Placarding (FMCSA), cylinder securing (upright), ventilation
(never in trunk/closed vehicle), leak checks before transit .
• Safety Devices & Emergency Response: Pressure relief valves, hydrostatic relief valves (liquid
expansion protection), ESV activation, emergency response plans, PPE (gloves, goggles, FR
clothing) .
• Site & Clearance Requirements: Dispenser to building (10 ft min), storage tank to building,
container placement .
• Piping & Fittings: Black steel (ASTM A53), copper Type L/G, prohibited materials (PVC, ABS),
fittings and valves .
• Personnel Certification: QP (Qualified Person) card, annual renewal, required knowledge for
LP-9 certification .
200 QUESTIONS (MCQs)
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1. What is the molecular formula of propane?
A) CH₄
B) C₂H₆
C) C₃H₈
D) C₄H₁₀
Answer: C) C₃H₈
Rationale: Propane is a three-carbon alkane with the formula C₃H₈. Methane is CH₄, ethane C₂H₆, and
butane C₄H₁₀ .
2. At atmospheric pressure, propane boils at approximately:
A) 32°F
B) –44°F
C) –10°F
D) 0°F
Answer: B) –44°F
Rationale: Propane’s boiling point is about –44°F (–42°C). This low boiling point allows propane to
remain liquid under moderate pressure at ambient temperatures .
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3. Which statement best describes how propane vapor pressure changes as temperature rises?
A) It decreases linearly
B) It remains constant
C) It increases exponentially
D) It increases slightly then drops
Answer: C) It increases exponentially
Rationale: Vapor pressure follows the Antoine equation; a small temperature rise causes a large increase
in pressure, which is why the 80% fill rule is critical .
4. The 80% fill rule for LP-Gas cylinders is primarily based on:
A) Specific gravity of liquid
B) Coefficient of thermal expansion of liquid propane
C) Boiling point of propane
D) Flash point of propane
Answer: B) Coefficient of thermal expansion of liquid propane
*Rationale: Liquid propane expands significantly with temperature (coefficient of thermal expansion
~0.002/°F). The 20% vapor space (ullage) allows for expansion without over-pressurizing the container .*
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5. What is the specific gravity of liquid propane (relative to water)?
A) 0.51
B) 1.52
C) 2.01
D) 0.82
Answer: A) 0.51
Rationale: Liquid propane has a specific gravity of approximately 0.51, meaning it is about half the
density of water. Vapor is about 1.5 times heavier than air .
6. Propane vapor is heavier than air. In a storage facility, leaked vapor will most likely accumulate:
A) Near the ceiling
B) At high windows
C) In low-lying pits or depressions
D) Around roof vents
Answer: C) In low-lying pits or depressions
*Rationale: Vapor density of propane is ~1.5 (air = 1). Leaked vapor sinks and collects in low areas,
creating a fire/explosion hazard .*
New Mexico (NM) LP‑9 Station for Dispensing LP‑Gas
Exam Actual Test Questions and Correct Answers With
Rationales LATEST THIS YEAR
EXAM COVERAGE (Point Form)
• LP-Gas Properties & Hazards: Chemical formula (C₃H₈), boiling point (–44°F), vapor pressure
(exponential with temp), specific gravity (liquid 0.5, vapor 1.5–2.0), flammability limits (2.1%–
9.5%), auto-ignition (530°F), odorant (ethyl mercaptan) .
• Container Construction & Identification: ASME vs. DOT specifications, water capacity stamps,
tare weight (TW), requalification dates (5-year visual, 12-year hydrostatic), OPD valves .
• Fill Limits & Gauging: 80% fill rule (liquid expansion), fixed liquid level gauge (spit valve/spitter),
bleeder valves, prevention of overfilling .
• Dispensing Equipment & Operation: Transfer hoses (rated min 350 psig), emergency shear
valves, excess-flow valves, bypass valves, breakaway devices, pump operation .
• NMAC & NFPA 58 Requirements: Self-service dispenser rules (ASME containers only, no DOT
cylinders), emergency shutdown devices, posted instructions, breakaway devices, annual QP
card renewal .
• Transportation & Vehicle Loading: Placarding (FMCSA), cylinder securing (upright), ventilation
(never in trunk/closed vehicle), leak checks before transit .
• Safety Devices & Emergency Response: Pressure relief valves, hydrostatic relief valves (liquid
expansion protection), ESV activation, emergency response plans, PPE (gloves, goggles, FR
clothing) .
• Site & Clearance Requirements: Dispenser to building (10 ft min), storage tank to building,
container placement .
• Piping & Fittings: Black steel (ASTM A53), copper Type L/G, prohibited materials (PVC, ABS),
fittings and valves .
• Personnel Certification: QP (Qualified Person) card, annual renewal, required knowledge for
LP-9 certification .
200 QUESTIONS (MCQs)
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1. What is the molecular formula of propane?
A) CH₄
B) C₂H₆
C) C₃H₈
D) C₄H₁₀
Answer: C) C₃H₈
Rationale: Propane is a three-carbon alkane with the formula C₃H₈. Methane is CH₄, ethane C₂H₆, and
butane C₄H₁₀ .
2. At atmospheric pressure, propane boils at approximately:
A) 32°F
B) –44°F
C) –10°F
D) 0°F
Answer: B) –44°F
Rationale: Propane’s boiling point is about –44°F (–42°C). This low boiling point allows propane to
remain liquid under moderate pressure at ambient temperatures .
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3. Which statement best describes how propane vapor pressure changes as temperature rises?
A) It decreases linearly
B) It remains constant
C) It increases exponentially
D) It increases slightly then drops
Answer: C) It increases exponentially
Rationale: Vapor pressure follows the Antoine equation; a small temperature rise causes a large increase
in pressure, which is why the 80% fill rule is critical .
4. The 80% fill rule for LP-Gas cylinders is primarily based on:
A) Specific gravity of liquid
B) Coefficient of thermal expansion of liquid propane
C) Boiling point of propane
D) Flash point of propane
Answer: B) Coefficient of thermal expansion of liquid propane
*Rationale: Liquid propane expands significantly with temperature (coefficient of thermal expansion
~0.002/°F). The 20% vapor space (ullage) allows for expansion without over-pressurizing the container .*
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5. What is the specific gravity of liquid propane (relative to water)?
A) 0.51
B) 1.52
C) 2.01
D) 0.82
Answer: A) 0.51
Rationale: Liquid propane has a specific gravity of approximately 0.51, meaning it is about half the
density of water. Vapor is about 1.5 times heavier than air .
6. Propane vapor is heavier than air. In a storage facility, leaked vapor will most likely accumulate:
A) Near the ceiling
B) At high windows
C) In low-lying pits or depressions
D) Around roof vents
Answer: C) In low-lying pits or depressions
*Rationale: Vapor density of propane is ~1.5 (air = 1). Leaked vapor sinks and collects in low areas,
creating a fire/explosion hazard .*
