UN 2591 — Xenon, refrigerated liquid (cryogenic liquid)
Placard: Non-Flammable Gas. ERG Guide 120. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Xenon, refrigerated liquid is an inert cryogenic material. The main hazards are cold burns, oxygen displacement and container pressure buildup during warming or fire exposure.
Hazard overview: Released liquid rapidly vaporizes and can displace air, especially indoors or in low areas. Direct contact can freeze tissue, and pressure relief devices must remain unobstructed.
Response guidance: Approach from upwind, monitor oxygen levels and ventilate only with trained personnel. Do not plug leaks, block relief devices or expose responders to cryogenic liquid; cool fire-exposed containers from a protected location.
Firefighter training notes: Train crews on cryogenic liquid behavior, oxygen monitoring, frostbite prevention and container pressure relief. Emphasize that inert gases can be fatal in confined spaces.
Regulatory context: UN 2591 is Xenon, refrigerated liquid, Class 2.2 nonflammable gas. Verify cylinder or cryogenic container markings and pressure relief status.
Storage & handling: Store upright in ventilated areas, secured from impact and heat. Keep relief devices unobstructed and protect containers from fire exposure.
UN 2591 Quick Details
Common Hazards of UN 2591
- Refrigerated cryogenic liquid; contact can cause severe frostbite and cold burns.
- Xenon gas can displace oxygen and create an asphyxiation hazard in confined or low areas.
- Rapid warming can increase pressure and rupture cylinders or cryogenic containers.
- Vapor cloud may be very cold and can condense atmospheric moisture, reducing visibility.
- Containers exposed to fire may fail from pressure buildup.
- Liquid can make some materials brittle, increasing equipment failure risk.
- Xenon is inert and nonflammable, but oxygen deficiency can occur without odor or warning.
Chemical Identity & Physical Properties
Refrigerated liquid xenon is a very cold, colorless cryogenic liquid that forms heavy gas as it warms. The gas is odorless and nonflammable.
| Also known as | XenonLiquid xenonCryogenic xenonLXeRefrigerated liquid xenon |
| CAS Number | 7440-63-3 |
| Appearance | Colorless, odorless cryogenic liquid or compressed gas. Boiling point is extremely low at -108°C (-162°F), creating dense white vapors upon release. |
| Flash Point | Not applicable (inert gas) |
| Boiling Point | -108C (-162F) |
| Vapor Density | 4.5 (heavier than air) |
| Water Reactivity | No chemical reaction with water expected; cryogenic contact with water or surfaces can cause freezing and pressure or visibility issues. |
Fireground Response Guidance — UN 2591
Extinguishing Media
PPE Requirements
Use SCBA in oxygen-deficient or unmonitored atmospheres. Cryogenic gloves, face shield and insulated protection are needed where liquid or cold vapor contact is possible.
Isolation & Evacuation
First Actions for a UN 2591 Incident
- Call 911 and the emergency response number shown on shipping papers; confirm the material with ERG, SDS and container markings.
- Keep unauthorized personnel away and establish hot, warm and cold zones before entry.
- Stay upwind, uphill and upstream; avoid low areas where vapors, dust or runoff may collect.
- Avoid breathing vapors, dust, mist or decomposition products and prevent skin or eye contact.
- Do not touch damaged packages or containers unless properly trained and wearing suitable chemical PPE.
- Ventilate confined spaces only after atmospheric monitoring and only with trained, equipped personnel.
- Use ERG Guide 120, SDS, shipping papers and monitoring results for isolation, PPE and fire-control decisions.
📋 Copy & Share Field Card
UN 2591 — Xenon, 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.