Hydrogen Sulfide

Classification

Flammable gas Cat 1; Gas under pressure (liquefied gas); Acute toxicity (inhalation) Cat 2; Aquatic acute Cat 1

Hazard statements

• H220 Extremely flammable gas.
• H280 Contains gas under pressure; may explode if heated.
• H330 Fatal if inhaled.
• H400 Very toxic to aquatic life.

Key precautionary statements

• P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
• P260 Do not breathe dust/fume/gas/mist/vapors/spray.
• P271 Use only outdoors or in a well-ventilated area.
• P284 In case of inadequate ventilation, wear respiratory protection.
• P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
• P316 Get emergency medical help immediately.
• P377 Leaking gas fire: Do not extinguish, unless leak can be stopped safely.
• P381 In case of leakage, eliminate all ignition sources.

In general industry, OSHA sets a 20 ppm ceiling (Table Z-2). A single peak up to 50 ppm is allowed for no more than 10 minutes once per 8-hour shift, and only if there is no other measurable exposure. OSHA's construction and shipyard PEL is 10 ppm as an 8-hour TWA. NIOSH recommends a 10 ppm ceiling over any 10 minutes, and ACGIH's TLV is much lower at 1 ppm TWA and 5 ppm STEL. Cal/OSHA is stricter than the federal limit, with 10 ppm TWA, 15 ppm STEL and a 50 ppm ceiling. Smell is not a reliable warning because the sense of smell tires quickly. State OSHA plans may set different limits.

• Appearance: Colorless gas, shipped as a liquefied compressed gas
• Odor: Rotten eggs; the sense of smell tires quickly and cannot be relied on to detect continued exposure
• Molecular weight: 34.1
• Boiling point: -77°F (-61°C)
• Freezing point: -122°F (-86°C)
• Flash point: Not applicable (flammable gas)
• Autoignition temperature: 500°F (260°C)
• Explosive limits: LEL 4.0%, UEL 44.0%
• Vapor pressure: 17.6 atm
• Relative gas density: 1.19 (heavier than air; collects in low areas)
• Water solubility: 0.4%

Inhalation

Irritates the eyes and respiratory system and causes headache, dizziness, weakness, irritability, insomnia and stomach upset. High concentrations act on the nervous system and can stop breathing, causing convulsions, coma and death within a very short time.

Skin

The gas is not a significant skin hazard, but contact with the liquefied gas can cause frostbite.

Eyes

Conjunctivitis, eye pain, tearing, sensitivity to light and blistering of the cornea. Liquid contact can cause frostbite.

Ingestion

Not an expected route of exposure for a gas.

Target organs

Eyes, respiratory system, central nervous system

Gloves

Chemical-resistant gloves selected using the manufacturer's permeation data. Where liquefied gas could be released, also protect hands against frostbite.

Eyes and face

Safety glasses with side shields where contact is possible; chemical goggles and protection against frostbite where liquid can be released.

Respiratory

Do not rely on smell; use gas detection. Up to 100 ppm, NIOSH lists a full-facepiece gas mask with a hydrogen sulfide canister, a powered air-purifying respirator, a supplied-air respirator or an SCBA. For rescue, emergencies or unknown levels, use a full-facepiece pressure-demand SCBA.

Clothing

Anti-static clothing where static ignition is a risk. Remove clothing promptly if it becomes wet with the liquid (flammable).

Store cylinders upright, secured and with valve caps in place, in a cool, dry, well-ventilated, locked area away from sunlight and incompatible materials. Do not let cylinder temperature exceed 125°F (52°C).

Use non-sparking tools and explosion-proof equipment. Move cylinders with a hand truck; do not drag, roll or drop them. Close the valve after each use. Treat sewers, pits, tanks and other confined spaces as places where the gas can build up.

Keep away from

• Strong oxidizers
• Strong nitric acid
• Metals

• Evacuate and isolate the leak area for at least 330 feet (100 meters) in all directions.
• Rescuers and responders must wear a positive-pressure SCBA.
• Eliminate all ignition sources and use non-sparking, grounded equipment.
• Stop the leak only if it is safe to do so. Use water spray to knock down vapors, but do not spray water directly on the leak.
• Keep gas out of sewers, basements and confined areas, and keep the area isolated until the gas has dispersed.
• Refer to ERG Guide 117 (UN1053).

Suitable extinguishing media

• Stop the flow of gas if it is safe to do so; if the leak cannot be stopped, let the fire burn
• Use an extinguishing agent suited to the surrounding fire
• For large fires, water spray, fog or foam
• Water spray to cool fire-exposed cylinders

Special hazards

Extremely flammable gas that is heavier than air and can travel to an ignition source. Cylinders can burst when heated. Burning produces toxic sulfur oxides. If a tank, rail car or tank truck is involved in a fire, isolate for 1 mile (1600 meters) in all directions. Firefighters need positive-pressure SCBA.

• OSHA Hazard Communication (29 CFR 1910.1200): Hazardous chemical; SDS, labels and training required.
• OSHA Air Contaminants (29 CFR 1910.1000 Table Z-2): 20 ppm ceiling; 50 ppm peak for up to 10 minutes once per shift if no other measurable exposure occurs.
• EPA CERCLA (40 CFR 302.4): Hazardous substance, reportable quantity 100 lb.
• EPA EPCRA Section 302 (40 CFR 355): Extremely hazardous substance, threshold planning quantity 500 lb; release reportable quantity 100 lb.
• EPA EPCRA Section 313 (TRI) (40 CFR 372.65): Listed.
• EPA Clean Air Act 112(r) (40 CFR 68.130): Regulated toxic substance, threshold quantity 10,000 lb.
• DOT (49 CFR 172.101): UN1053, Hydrogen sulfide, Division 2.3 with 2.1 subsidiary hazard, Inhalation Hazard Zone B.

• NIOSH Pocket Guide to Chemical Hazards: Hydrogen sulfide
• OSHA Occupational Chemical Database: Hydrogen sulfide
• PubChem: Hydrogen sulfide (CID 402)
• NOAA CAMEO Chemicals: Hydrogen sulfide
• Airgas SDS: Hydrogen sulfide