Hydrogen Sulfide
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þ A good resource for information about exposure to hazardous materials, such
as hydrogen sulfide, is the textbook "Hazardous Materials Toxicology:
Clinical Principles of Environmental Health" edited by John B. Sullivan, Jr
and Gary R. Krieger, published by Williams and Wilkins.

Regarding hydrogen sulfide, the IDHL (immediately dangerous to health or
life) for rabbits is 300 ppm, and the toxic concentration 125 ppm (adjusted
from a 90 minute exposure). IDHL levels are based on a 30 minute exposure.
Emergency Exposure Guidance Levels (EEGL) developed by the National Academy
of Sciences for military personnel to prevent injury, and based on one hour
exposures, list hydrogen sulfide EEGL levels at 50 ppm. The rotten egg odor
is perceptible at 0.13 ppm; A concentration of 20 ppm is safe for 7 hr.
exposure (CRC Crit Rev Toxicol 1984;13:25-97). Eye and respiratory tract
irritation is noticeable at 50 ppm, olfactory fatigue at 100 ppm, olfactory
nerve paralysis at 150 ppm, dizziness/respiratory depression at 500 ppm, loss
of consciousness at 700 ppm, respiratory paralysis at 1000 ppm. Hydrogen
sulfide is also known for having a high rescuer to victim fatality ratio,
i.e., many would-be rescuers die while trying to rescue victims of hydrogen
sulfide exposure.

Hope this helps!

Nici Singletary, MD, FACEP
Associate Professor, Emergency Medicine
Eastern Virginia Medical School
Norfolk, VA