UN/NA Number Reference
DOT Class 2.2 Non-Flammable Gas placard

UN 1977: Nitrogen, refrigerated liquid

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1977 is assigned the proper shipping name Nitrogen, refrigerated liquid in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 2.2 Non-Flammable Gas material. Required label(s): 2.2.

Packing group indicates the degree of danger within a hazard class: PG I is high danger, PG II medium, PG III low. The proper shipping name, hazard class, UN number, and packing group together form the basic shipping description that must appear on shipping papers and, where required, on the package and placard.

Emergency Response (ERG Guide 120)

Hazards: Vapors may cause dizziness or asphyxiation. Contact with liquid may cause frostbite. Containers may rocket if heated.

Fire: Use agent appropriate for surrounding fire. Cool containers with water.

Spill: Do not touch. Stop leak if safe. Use water spray to reduce vapor. Ventilate area.

Chemical and Physical Properties

Nitrogen appears as a colorless odorless gas. Noncombustible and nontoxic. Makes up the major portion of the atmosphere, but will not support life by itself. Used in food processing, in purging air conditioning and refrigeration systems, and in pressurizing aircraft tires. May cause asphyxiation by displacement of air. Under prolonged exposure to fire or heat containers may rupture violently and rocket.

CAS Number: 7727-37-9
Molecular Formula: N2
Molecular Weight: 28.014 g/mol
Color / Form: Colorless gas
Odor: Odorless gas
Boiling Point: -320.1 °F
Melting Point: -354 °F (USCG, 1999)
Specific Gravity: 0.807 (floats on water)
Vapor Pressure: -236 °C at 1Pa (solid); -232 °C at 10Pa (solid); -226.8 °C a
Vapor Density: 0.96737 (lighter than air)
Water Solubility: In water, 1.81X10+4 mg/L at 21 °C
Log P: log Kow = 0.67

Special Provisions

49 CFR 172.102 special provision codes for this entry: 345, 346, T75, TP5. These codes modify the general requirements (packaging, quantity limits, exceptions) for this specific material. Look up each code in 49 CFR 172.102 for the full text.

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Reference data compiled from the DOT Hazardous Materials Table (49 CFR 172.101), the 2024 Emergency Response Guidebook, and public chemical databases (PubChem, NIOSH, EPA). Always verify the correct shipping description against the current regulation and the manufacturer's SDS Section 14 before shipping.