LG Liquefied Gases Examination

Coast Guard Tankerman–Person in Charge (LG – Liquefied Gases) Examination Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which is the primary hazard associated with liquefied gases?
• Fire
• Explosion
• Electrocution
• Slips and falls

Liquefied gases are stored under pressure and can vaporize rapidly, creating explosive mixtures.

• What is the minimum distance required between a liquefied gas

transfer operation and a building?

• 10 feet
• 25 feet 1 / 4

• 50 feet
• 100 feet

Safety regulations require at least 50 feet to minimize the risk of fire or explosion near structures.

• When transferring liquefied gases, which type of hose is required?
• Rubber garden hose
• PVC hose
• Approved liquefied gas hose
• Nylon rope

Only hoses designed and rated for liquefied gas service should be used to handle pressure and chemical compatibility.

• Which device is used to relieve excess pressure in a liquefied gas tank?
• Pump
• Gauge
• Pressure relief valve
• Thermometer

Pressure relief valves are designed to prevent tank rupture by releasing excess pressure safely.

• Which class of flammable gases do most liquefied gases fall under?
• Class 1
• Class 2
• Class 2.1
• Class 3 2 / 4

Most liquefied flammable gases are Class 2.1 according to DOT classification.

• Which personal protective equipment (PPE) is essential when handling

liquefied gases?

• Hard hat only
• Gloves only
• Gloves, face shield, and chemical-resistant suit
• Ear plugs only

Cryogenic and toxic gases can cause severe burns or frostbite, so full protective gear is necessary.

• What is the primary concern when liquefied gas comes in contact with

water?

• Freezing
• Rapid vaporization and potential explosion
• Cooling effect
• Neutralization

Liquefied gases can flash into vapor and expand rapidly when in contact with water.

• During a transfer, you notice the cargo tank is overfilling. What should

you do first?

• Ignore it
• Stop the transfer immediately
• Increase pumping speed 3 / 4

• Vent the gas manually

Overfilling can lead to spills, excessive pressure, or vapor release; immediate action is required.

• What is the primary method of detecting a liquefied gas leak?
• Sight only
• Leak detection sensors or soap solution
• Thermometer
• Pressure gauge only

Specialized detectors or soap solutions are used to identify leaks in pressurized systems.

10. The lower flammable limit (LFL) of a gas refers to:

• Maximum safe concentration
• Minimum concentration that can ignite
• Concentration for comfort
• Maximum pressure allowed

Below the LFL, the gas-air mixture cannot ignite.

• What is the purpose of a gas detector in a cargo area?
• To measure temperature
• To alert personnel of flammable or toxic gas presence
• To control pressure
• To lubricate valves

Gas detectors provide early warning to prevent fire, explosion, or exposure hazards.

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