The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is
stinkdamp. Hydrogen sulfide is a highly
toxic and flammable gas (
flammable range: 4.3–46%). It can poison several systems in the body, although the
nervous system is most affected. The toxicity of is comparable with that of
carbon monoxide. It binds with
iron in the
mitochondrial
cytochrome enzymes, thus preventing
cellular respiration. Its toxic properties were described in detail in 1843 by
Justus von Liebig. Even before hydrogen sulfide was discovered, Italian physician
Bernardino Ramazzini hypothesized in his 1713 book
De Morbis Artificum Diatriba that occupational diseases of sewer-workers and blackening of coins in their clothes may be caused by an unknown invisible volatile acid (moreover, in late 18th century toxic gas emanation from
Paris sewers became a problem for the citizens and authorities). Although very pungent at first (it smells like rotten eggs), it quickly deadens the sense of smell, creating temporary
anosmia, so victims may be unaware of its presence until it is too late. Safe handling procedures are provided by its
safety data sheet (SDS).
Low-level exposure Since hydrogen sulfide occurs naturally in the body, the environment, and the gut, enzymes exist to metabolize it. At some threshold level, believed to average around 300–350 ppm, the oxidative enzymes become overwhelmed. Many personal safety gas detectors, such as those used by utility, sewage and petrochemical workers, are set to alarm at as low as 5 to 10 ppm and to go into high alarm at 15 ppm. Metabolism causes oxidation to sulfate, which is harmless. Hence, low levels of hydrogen sulfide may be tolerated indefinitely. Exposure to lower concentrations can result in
eye irritation, a sore throat and
cough, nausea, shortness of breath, and
fluid in the lungs. These symptoms usually subside in a few weeks. Long-term, low-level exposure may result in
fatigue, loss of appetite,
headaches, irritability, poor memory, and
dizziness. Chronic exposure to low level (around 2
ppm) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers, but the reports have not (as of 1995) been replicated.
High-level exposure Short-term, high-level exposure can induce immediate collapse, with loss of breathing and a high probability of death. If death does not occur, high exposure to hydrogen sulfide can lead to
cortical pseudolaminar necrosis, degeneration of the
basal ganglia and
cerebral edema. Inhalation of resulted in about 7 workplace deaths per year in the U.S. (2011–2017 data), second only to carbon monoxide (17 deaths per year) for workplace chemical inhalation deaths.
Exposure thresholds • Exposure limits stipulated by the United States government: • 10
ppm REL-Ceiling (
NIOSH): recommended permissible exposure ceiling (the recommended level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs) • 20 ppm
PEL-Ceiling (
OSHA): permissible exposure ceiling (the level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs) • 50 ppm PEL-Peak (OSHA): peak permissible exposure (the level that must never be exceeded) • 100 ppm
IDLH (NIOSH): immediately dangerous to life and health (the level that interferes with the ability to escape) • 0.00047 ppm or 0.47
ppb is the odor threshold for hydrogen sulfide, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it. • 0.0047 ppm or 4.7 ppb is the recognition threshold, the point at which 50% of a human panel can identify the presence of hydrogen sulfide. • 10–20 ppm is the borderline concentration for eye irritation. • 50–100 ppm leads to eye damage. • At 100–150 ppm the
olfactory nerve is paralyzed after a few inhalations, and the
sense of smell disappears, often together with awareness of danger. • 320–530 ppm leads to
pulmonary edema with the possibility of death.
Incidents Hydrogen sulfide was used by the
British Army as a
chemical weapon during
World War I. It was not considered to be an ideal war gas, partially due to its flammability and because the distinctive smell could be detected from even a small leak, alerting the enemy to the presence of the gas. It was nevertheless used on two occasions in 1916 when other gases were in short supply. A dump of toxic waste containing hydrogen sulfide is believed to have caused 17 deaths and thousands of illnesses in
Abidjan, on the
West African coast, in the
2006 Ivory Coast toxic waste dump. In September 2008, three workers were killed and two suffered serious injury, including long term brain damage, at a mushroom growing company in
Langley,
British Columbia. A valve to a pipe that carried chicken
manure,
straw and
gypsum to the compost fuel for the mushroom growing operation became clogged, and as workers unclogged the valve in a confined space without proper ventilation the hydrogen sulfide that had built up due to anaerobic decomposition of the material was released, poisoning the workers in the surrounding area. An investigator said there could have been more fatalities if the pipe had been fully cleared and/or if the wind had changed directions. In 2014, levels of hydrogen sulfide as high as 83 ppm were detected at a recently built mall in
Thailand called Siam Square One at the
Siam Square area. Shop tenants at the mall reported health complications such as sinus inflammation, breathing difficulties and eye irritation. After investigation it was determined that the large amount of gas originated from imperfect treatment and disposal of waste water in the building. In 2014, hydrogen sulfide gas killed workers at the Promenade shopping center in North
Scottsdale, Arizona, USA after climbing into 15 ft deep chamber without wearing
personal protective gear. "Arriving crews recorded high levels of
hydrogen cyanide and hydrogen sulfide coming out of the sewer." In November 2014, a substantial amount of hydrogen sulfide gas shrouded the central, eastern and southeastern parts of
Moscow. Residents living in the area were urged to stay indoors by the emergencies ministry. Although the exact source of the gas was not known, blame had been placed on a Moscow oil refinery. In June 2016, a mother and her daughter were found dead in their still-running 2006
Porsche Cayenne SUV against a guardrail on
Florida's Turnpike, initially thought to be victims of
carbon monoxide poisoning. Their deaths remained unexplained as the medical examiner waited for results of toxicology tests on the victims, until urine tests revealed that hydrogen sulfide was the cause of death. A report from the Orange-Osceola Medical Examiner's Office indicated that toxic fumes came from the Porsche's
starter battery, located under the front passenger seat. In January 2017, three utility workers in
Key Largo, Florida, died one by one within seconds of descending into a narrow space beneath a
manhole cover to check a section of paved street. In an attempt to save the men, a firefighter who entered the hole without his air tank (because he could not fit through the hole with it) collapsed within seconds and had to be rescued by a colleague. The firefighter was airlifted to
Jackson Memorial Hospital and later recovered. A Monroe County Sheriff officer initially determined that the space contained hydrogen sulfide and
methane gas produced by decomposing vegetation. On May 24, 2018, two workers were killed, another seriously injured, and 14 others hospitalized by hydrogen sulfide inhalation at a
Norske Skog paper mill in
Albury, New South Wales. An investigation by
SafeWork NSW found that the gas was released from a tank used to hold
process water. The workers were exposed at the end of a 3-day maintenance period. Hydrogen sulfide had built up in an upstream tank, which had been left stagnant and untreated with
biocide during the maintenance period. These conditions allowed sulfate-reducing bacteria to grow in the upstream tank, as the water contained small quantities of
wood pulp and
fiber. The high rate of pumping from this tank into the tank involved in the incident caused hydrogen sulfide gas to escape from various openings around its top when pumping was resumed at the end of the maintenance period. The area above it was sufficiently enclosed for the gas to pool there, despite not being identified as a
confined space by Norske Skog. One of the workers who was killed was exposed while investigating an apparent fluid leak in the tank, while the other who was killed and the worker who was badly injured were attempting to rescue the first after he collapsed on top of it. In a resulting
criminal case, Norske Skog was accused of failing to ensure the health and safety of its workforce at the plant to a reasonably practicable extent. It pleaded guilty, and was fined AU$1,012,500 and ordered to fund the production of an anonymized educational video about the incident. In October 2019, an
Odessa, Texas employee of Aghorn Operating Inc. and his wife were killed due to a water pump failure.
Produced water with a high concentration of hydrogen sulfide was released by the pump. The worker died while responding to an automated phone call he had received alerting him to a mechanical failure in the pump, while his wife died after driving to the facility to check on him. A
CSB investigation cited lax safety practices at the facility, such as an informal
lockout-tagout procedure and a nonfunctioning hydrogen sulfide alert system. On April 22, 2026,
A leak in Institute, West Virginia occurred. 2 deaths resulted from the accident, along with 27 hospitalized.
Suicides The gas, produced by mixing certain household ingredients, was used in a
suicide wave in 2008 in Japan. The wave prompted staff at Tokyo's
suicide prevention center to set up a special hotline during "
Golden Week", as they received an increase in calls from people wanting to kill themselves during the annual May holiday. As of 2010, this phenomenon has occurred in a number of US cities, prompting warnings to those arriving at the site of the suicide. In 2020, ingestion was used as a suicide method by Japanese pro wrestler
Hana Kimura. In 2024, Lucy-Bleu Knight, stepdaughter of famed musician
Slash, also used ingestion to commit suicide. ==Hydrogen sulfide in the natural environment==