UN/NA Number Reference

UN 2509: Hydrogen sulfide

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2509 is assigned the proper shipping name Hydrogen sulfide 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, 2.1.

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 117)

Hazards: TOXIC. May be fatal if inhaled. Extremely flammable. Vapors heavier than air.

Fire: Do not extinguish unless flow stopped. Water spray to cool containers. Fight from maximum distance.

Spill: Fully encapsulating gas-tight suits required. Do not touch. Stop leak if safe.

Chemical and Physical Properties

Hydrogen sulfide appears as a colorless gas having a strong odor of rotten eggs. Boiling point -60.2 °C. Shipped as a liquid confined under its own vapor pressure. Density (liquid) 8.3 lb / gal. Contact with the unconfined liquid can cause frostbite by evaporative cooling. Gas is very toxic by inhalation. Fatigues the sense of smell which cannot be counted on to warn of the continued presence of the gas. Prolonged exposure of closed containers to heat may result in their violent rupturing and rocketing. Rate of onset: Immediate & Delayed Persistence: Minutes to hours Odor threshold: 0.1 ppm Source/use/other hazard: Disinfectant lubricant/oils; interm for HC manufacture; deadens sense of smell.

CAS Number: 7783-06-4

Molecular Formula: H2S

Molecular Weight: 34.08 g/mol

Color / Form: Colorless gas [Shipped as a liquefied compressed gas].

Odor: Strong odor of rotten eggs [Note: Sense of smell becomes rapidly fatigued & can NOT be relied upon to warn of the continuous presense of hydrogen sulfide].

Boiling Point: -76.59 F

Melting Point: -121.9 °F (EPA, 1998)

Flash Point: 500 F

Autoignition: 500 °F (USCG, 1999)

Specific Gravity: 0.916 at -76 F

Vapor Pressure: 15200 mmHg at 77.9 F

Vapor Density: 1.19 (heavier than air)

Water Solubility: 0.4 %

pH: pH freshly prepared water soln: 4.5

Regulatory Data

CERCLA RQ (40 CFR 302.4)

100 lb

EPCRA TPQ (40 CFR 355)

500 lb

OSHA PEL

See Annotated Z-2 See Annotated Z-2 HYDROGEN SULFIDE - ACGIH

NIOSH REL

C 10 ppm (15 mg/m 3 ) [10-minute]

IDLH

100 ppm

RCRA Waste Code(s)

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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: A7, IB8, IP2, IP4, N34, T3, TP33. 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.