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.
UN 2591 At a Glance
UN 2591 (Xenon, refrigerated liquid (cryogenic liquid)) is listed as DOT Class 2 Non-Flammable Gas and is assigned to ERG Guide 120. Use this page to review placard data, common hazards, PPE notes, isolation context, first actions, and related UN numbers.
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.