Although hydrogen sulfide possesses important roles in certain physiological functions of the human body, hydrogen sulfide poisoning is regarded as one of the most common intoxications by a gas in the occupational settings. This compound causes acute toxicity of the lungs and central nervous system, producing manifestations such as a headache, dizziness, changes in consciousness, and respiratory depression with hypoxemia. History taking is crucial for determining exposure to this gas, whereas a confirmation of elevated hydrogen sulfide concentrations is achieved through specialized biochemical tests.
Signs and symptoms of hydrogen sulfide poisoning stem from the contact with very high concentrations of this colorless gas (mainly through inhalation) which causes disruption of adenosine triphosphate (ATP) production in the mitochondria    . Most cases of poisoning occur in the occupational settings and after carbon monoxide (CO), hydrogen sulfide (H2S) is the second most common cause of work-related death due to gas poisoning . Individuals involved in agriculture, sewage processing, or those who are in regular contact with petroleum have shown to be exposed to significant concentrations of this gas  . On the other hand, active volcanoes are a natural source of H2S, meaning that people living in the proximity of volcanoes may also be at risk . Moreover, suicides or intentional poisoning (hydrogen sulfide is listed as a chemical weapon) have also been reported  . Hydrogen sulfide poisoning manifests acutely in most cases. The central nervous system (CNS) and the respiratory system (lungs) are the two main organ systems where hydrogen sulfide exerts its toxic effects  . Headaches, nausea, vomiting, changes in coordination, and even loss of consciousness are frequent manifestations, while pulmonary edema with subsequent hypoxemia and respiratory depression are main findings involving the respiratory system  . Because H2S is able to block calcium channels in the heart, cardiac function can be impaired and lead to ventricular fibrillation or even death from cardiogenic shock in some patients   .
A detailed patient history is the essential part of the diagnostic workup in patients with hydrogen sulfide poisoning. The physician needs to cover the course of symptoms, their progression, and determine if they may have occurred as a result of exposure at the workplace. If there is suspicion of intentional poisoning, a heterogeneous anamnesis from parents, close relatives, partners, or friends might be useful. A physical examination can further reveal neurological impairment, cardiac disturbances, and respiratory difficulties.
Spirometry, electrocardiography, as well as measurements of blood pressure and echocardiography, are important features of hydrogen sulfide poisoning workup, but significant changes may not always be present   . In order to make a definite diagnosis, specific biochemical tests need to be employed. Gas chromatography-mass spectrometry (GC-MS), a tool that is able to detect the concentration of many substances including gases, is the promising method for the diagnosis of hydrogen sulfide poisoning  . Blood and urine are used as samples for a measurement of hydrogen sulfide metabolites .