Practice Exam Questions And Correct

FDNY W79 — Delivering, Installing, Repairing Cryogenic Containers or Systems Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary hazard associated with cryogenic liquids?
• Chemical reactivity
• Extreme cold (cryogenic burns / cold thermal hazard)
• Corrosive fumes
• Electrical shock

Because cryogenic liquids are extremely cold, direct contact causes severe cold burns and material embrittlement.

• Which of the following gases is commonly stored as a cryogenic liquid?
• Carbon dioxide
• Propane
• Liquid nitrogen (LN2)
• Natural gas (methane) 1 / 4

Liquid nitrogen is a commonly used cryogenic liquid for industrial and medical uses and is stored at very low temperatures.

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

cryogenic liquids?

• Cotton gloves and sneakers
• Cryogenic gloves, face shield, eye protection, and apron
• Regular latex gloves and sunglasses
• High-visibility vest only

Specialized cryogenic gloves and full face/eye protection protect against splash and cold transfer.

• Which property describes cryogenic liquids expanding rapidly into gas

when warmed?

• Low viscosity
• High density
• High volumetric expansion ratio (liquid to gas)
• High electrical conductivity

Cryogenic liquids have very large expansion ratios, so a small liquid leak can create large gas volumes, posing asphyxiation and pressure hazards.

• What is the function of a pressure-relief device on a cryogenic

container?

• Filter impurities
• Add pressure to the container 2 / 4

• Prevent overpressure by venting excess gas safely
• Heat the liquid to prevent freezing

Relief devices vent gas to prevent container rupture from thermal or vapor pressure buildup.

• Which of these is the safest way to transfer cryogenic liquid from a

tanker to a storage vessel?

• Pouring by hand
• Using approved transfer hoses and properly bonded couplings

with pressure-equalizing procedures

• Using garden hoses
• Transferring in open containers at ground level

Approved hoses and couplings control flow and limit leaks; bonding and correct procedures reduce hazards from spillage and pressure differences.

• What hazard does oxygen enrichment present during cryogenic

operations?

• Reduced flammability of materials
• Increased fire risk — materials ignite more easily and burn hotter
• Slower chemical reactions
• Neutralizes combustibles

Higher oxygen concentrations dramatically increase fire risk; materials normally safe can ignite easily. 3 / 4

• Which detector is most important to protect personnel from oxygen-

deficient atmospheres in a cryogenic storage area?

• Carbon monoxide detector
• Smoke detector
• Oxygen (O₂) monitor/alarm
• Ultraviolet detector

Oxygen monitors detect hypoxic atmospheres caused by cryogen vapor displacement of air and warn occupants.

• What is the correct action if a transfer hose begins to leak during fill?
• Tighten with bare hands immediately
• Ignore and continue filling
• Shut down transfer, isolate line, evacuate area if necessary, and

follow spill response plan

• Pour water on the leak to freeze it shut

Stopping flow and isolating the leak prevents escalation; water can create additional hazards with cryogens.

• Which valve type is commonly used for isolation in cryogenic

systems because of low leakage?

• Globe valve only
• Ball valve rated for cryogenic service
• Non-rated butterfly valve
• Ordinary gate valve without cryogenic rating
• / 4