UN 1977 — Nitrogen, 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 1977 is Nitrogen, refrigerated liquid (cryogenic liquid), a non-flammable cryogenic liquid assigned to ERG Guide 120. It can displace oxygen without warning and cause severe cold burns.
Hazard overview: 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. Cold nitrogen vapor is initially heavier than air and may collect in low or confined areas.
Response guidance: For a UN 1977 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 1977 should emphasize pressure hazards, oxygen displacement, frostbite, cylinder rupture/rocket risk, ventilation and atmospheric monitoring. Use ERG 120, SDS and local SOP.
Regulatory context: Nitrogen, refrigerated liquid (cryogenic liquid) is regulated as a hazardous material for transportation and emergency response purposes. Storage, workplace exposure, emergency planning, spill reporting and waste handling requirements 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: Nitrogen, 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 and oxygen/flammable gas monitoring where appropriate.
UN 1977 Quick Details
Common Hazards of UN 1977
- 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.
- Cold nitrogen vapor is initially heavier than air and may collect in low or confined areas.
- Rapid vaporization can create pressure buildup and cold vapor clouds near the release.
- 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 (-196°C) producing colorless, odorless gas that is heavier than air when cold.
| Also known as | Liquid nitrogenLN2LINCryogenic nitrogenNitrogen (liquefied) |
| CAS Number | 7727-37-9 |
| Appearance | Colorless, odorless cryogenic liquid. Boils at extremely low temperature (-196°C) producing colorless, odorless gas that is heavier than air when cold. |
| Flash Point | Not applicable (non-flammable gas) |
| Boiling Point | -196°C (-320°F) at atmospheric pressure |
| Vapor Density | 0.97 (lighter than air when warm); cold vapors initially heavier than air |
| Water Reactivity | No significant reaction; extreme cold may cause water to freeze |
Fireground Response Guidance — UN 1977
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 1977 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 vapors, gas, smoke, mist or dust and avoid skin or eye contact.
- Protect against cryogenic frostbite and avoid low/confined areas until oxygen and 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 or spill area and expand the perimeter for fire involvement, vapor accumulation, cylinder/tank heating or unknown product identity.
- Use ERG Guide 120, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1977 — Nitrogen, refrigerated liquid (cryogenicUse 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.