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

UN 2073: Ammonia, solution

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2073 is assigned the proper shipping name Ammonia, solution 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 125)

Hazards: TOXIC. Corrosive. Causes burns. May be fatal if inhaled. Vapors heavier than air.

Fire: Use water spray or fog. Do not get water inside containers.

Spill: Fully encapsulating suit required. Stop leak if safe. Use water spray.

Chemical and Physical Properties

Ammonia solutions (containing more than 35% but not more than 50% ammonia) appears as a clear colorless liquid consisting of ammonia dissolved in water. Corrosive to tissue and metals. Although ammonia is lighter than air, the vapors from a leak will initially hug the ground. Long term exposure to low concentrations or short term exposure to high concentrations may result in adverse health conditions from inhalation. Prolonged exposure of containers to fire or heat may result in their violent rupturing and rocketing.

CAS Number: 7664-41-7
Molecular Formula: H3N
Molecular Weight: 17.031 g/mol
Color / Form: Colorless gas
Odor: Sharp, cloying, repellent
Boiling Point: -28.03 °F at 760 mmHg (EPA, 1998)
Melting Point: -107.9 °F (EPA, 1998)
Flash Point: 132 °C (270 °F) - closed cup
Autoignition: 1204 °F (USCG, 1999)
Specific Gravity: 0.6818 at -28.03 °F (EPA, 1998) - Less dense than water; will float
Vapor Pressure: 400 mmHg at -49.72 °F (EPA, 1998)
Vapor Density: 0.6 (EPA, 1998) - Lighter than air; will rise (Relative to Air)
Water Solubility: 34 % (NIOSH, 2024)
Log P: log Kow = -2.66 /estimate for ammonium hydroxide which is the form of ammonia in water/
pH: pH of 1.0N aqueous solution 11.6; 0.1N aqueous solution 11.1; 0.01N aqueous solution 10.6

Regulatory Data

CERCLA RQ (40 CFR 302.4)
100 lb
EPCRA TPQ (40 CFR 355)
500 lb
OSHA PEL
50 35 25 ppm (ST) 35 ppm
NIOSH REL
TWA 25 ppm (18 mg/m 3 ) ST 35 ppm (27 mg/m 3 )
IDLH
300 ppm

A release of this material at or above its CERCLA reportable quantity (100 lb) requires immediate notification to the National Response Center at 800-424-8802.

Special Provisions

49 CFR 172.102 special provision codes for this entry: N87. 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.