LABORATORY CHEMICAL SAFETY SUMMARY: HYDROGEN SULFIDE

Substance

Hydrogen sulfide

(Hydrosulfuric acid, sulfur hydride)

CAS 7783-06-4

 

Formula

H2S

 

Physical Properties

Colorless gas

bp -61 °C, mp -83 °C

Slightly soluble in water (2.9 g/100 mL at 20 °C)

 

Odor

Strong rotten egg odor detectable at 0.001 to 0.1 ppm (mean = 0.0094 ppm); olfactory fatigue occurs quickly at high concentrations

Vapor Density

1.189 (air = 1.0)

 

Vapor Pressure

20 atm at 25 °C

 

Flash Point

< -82.4 °C

 

Autoignition Temperature

260 °C

 

Toxicity Data

LC50 inhal (rat)

444 ppm (580 mg/m3)

 

LCLO inhal (human)

800 ppm (1110 mg/m3; 5 min)

 

PEL (OSHA)

20 ppm (ceiling) (28 mg/m3)

 

TLV-TWA (ACGIH)

10 ppm (14 mg/m3)

 

STEL (ACGIH)

15 ppm (21 mg/m3)

Major Hazards

Moderately toxic gas; inhalation of large concentrations can cause unconsciousness, respiratory paralysis, and death; highly flammable.

Toxicity

The acute toxicity of hydrogen sulfide by inhalation is moderate. A 5-min exposure to 800 ppm has resulted in death. Inhalation of 1000 to 2000 ppm may cause coma after a single breath. Exposure to lower concentrations may cause headache, dizziness, and upset stomach. Low concentrations of H2S (20 to 150 ppm) can cause eye irritation, which may be delayed in onset. Although the odor of hydrogen sulfide is detectable at very low concentrations, it rapidly causes olfactory fatigue at higher levels, and therefore is not considered to have adequate warning properties.

Hydrogen sulfide has not been shown to be carcinogenic or to have reproductive or developmental effects in humans.

Flammability and Explosibility

Hydrogen sulfide is flammable in air in the range of 4.3 to 45.5% (NFPA rating = 4). Combustion products (sulfur oxides) are also toxic by inhalation. In the event of a hydrogen



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