UN/NA Number Reference
DOT Class 2.3 Toxic Gas placard

UN 1079: Sulfur dioxide

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1079 is assigned the proper shipping name Sulfur dioxide in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 2.3 Toxic Gas material. Required label(s): 2.3.

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

Sulfur dioxide appears as a colorless gas with a choking or suffocating odor. Boiling point -10 °C. Heavier than air. Very toxic by inhalation and may irritate the eyes and mucous membranes. Under prolonged exposure to fire or heat the containers may rupture violently and rocket. Used to manufacture chemicals, in paper pulping, in metal and food processing. Rate of onset: Immediate & Delayed Persistence: Minutes to hours Odor threshold: 1 ppm Source/use/other hazard: Disinfectant and preserving in breweries and food/canning; textile industry; batteries.

CAS Number: 7446-09-5
Molecular Formula: O2S
Molecular Weight: 64.07 g/mol
Color / Form: Colorless gas or liquid
Odor: Strong suffocating odor
Boiling Point: 14 F
Melting Point: -98.9 °F (EPA, 1998)
Autoignition: Not flammable (USCG, 1999)
Specific Gravity: 1.434 (sinks in water)
Vapor Pressure: 2432 mmHg at 68 F
Vapor Density: 2.26 (heavier than air)
Water Solubility: 10 %

Regulatory Data

CERCLA RQ (40 CFR 302.4)
1 lb
EPCRA TPQ (40 CFR 355)
500 lb
OSHA PEL
TWA 5 ppm (13 mg/m 3 )
NIOSH REL
TWA 2 ppm (5 mg/m 3 ) ST 5 ppm (13 mg/m 3 )
IDLH
100 ppm

A release of this material at or above its CERCLA reportable quantity (1 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: 3, B14, T50, TP19. 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.

Need the full interactive record? Open UN 1079 in the SpillNerd lookup tool for the live database entry with placard graphics, GHS pictograms, full segregation tables, and synonym search. For another material, use the UN number and chemical lookup.

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.