UN 1951 — Argon, refrigerated liquid (cryogenic liquid)
Placard: Non-Flammable Gas. ERG Guide 120. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1951 is Argon, refrigerated liquid (cryogenic liquid), a non-flammable cryogenic inert gas assigned to ERG Guide 120. It can displace oxygen without warning and cause severe cryogenic burns.
Hazard overview: UN 1951 presents asphyxiation, frostbite, cold vapor cloud and pressure/container rupture hazards.
Response guidance: For a UN 1951 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 120. Establish incident command, isolate the area, stay upwind, control ignition or downwind hazards, cool exposed containers from a protected distance when appropriate and base entry decisions on monitoring and local SOP.
Firefighter training notes: Training for UN 1951 should emphasize pressure hazards, oxygen displacement, frostbite, cylinder rupture/rocket risk, ventilation and atmospheric monitoring. Use ERG 120, SDS and local SOP.
Regulatory context: Argon, refrigerated liquid (cryogenic liquid) is regulated as a hazardous material for transportation and emergency response purposes. Requirements for storage, workplace exposure, emergency planning, spill reporting and waste handling vary by exact product, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, container markings and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Argon, refrigerated liquid (cryogenic liquid) should be stored in approved cryogenic containers in a ventilated area away from heat, ignition sources where flammable, confined low spots and physical damage. Provide pressure relief, oxygen/flammable gas monitoring where appropriate and cryogenic handling controls.
UN 1951 Quick Details
Common Hazards of UN 1951
- NON-FLAMMABLE cryogenic inert gas; vapor may displace oxygen and cause asphyxiation without warning.
- Contact with refrigerated liquid or cold vapor can cause severe frostbite and cryogenic burns.
- Rapid vaporization can create pressure buildup and cold vapor clouds near the release.
- Gas is odorless and inert, so oxygen deficiency may not be noticed by responders.
- Containers may rupture or rocket when heated or over-pressurized.
- Cold liquid can embrittle some materials and damage equipment.
- Ventilation and oxygen monitoring are critical in confined or low areas.
Chemical Identity & Physical Properties
Colorless, odorless cryogenic liquid. Boils at extremely low temperature (-186°C). Vapor is colorless and odorless, denser than air when cold.
| Also known as | Liquid argonLArCryogenic argonRefrigerated argonArgon gas liquefied |
| CAS Number | 7440-37-1 |
| Appearance | Colorless, odorless cryogenic liquid. Boils at extremely low temperature (-186°C). Vapor is colorless and odorless, denser than air when cold. |
| Flash Point | Not applicable (inert gas) |
| Boiling Point | -186°C (-303°F) |
| Vapor Density | 1.38 (heavier than air when cold) |
| Water Reactivity | No reaction - inert gas, but cryogenic temperature can cause violent boiling of water |
Fireground Response Guidance — UN 1951
Extinguishing Media
PPE Requirements
Use SCBA and oxygen monitoring in confined or oxygen-deficient areas. Wear face shield, insulated or cryogenic gloves and protective clothing when liquefied or refrigerated gas contact is possible.
Isolation & Evacuation
First Actions for a UN 1951 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing gas, vapor, smoke or mist and avoid skin or eye contact.
- Protect against cryogenic frostbite and avoid low/confined areas until oxygen and flammable gas readings are checked.
- Do not touch damaged containers or spilled/released material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the release area and expand the perimeter for fire involvement, cylinder heating, vapor accumulation, unknown gas identity or downwind exposure.
- Use ERG Guide 120, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1951 — Argon, refrigerated liquid (cryogenic liUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.