Hydrogen sulfide is a colorless, peculiarly smelling gas, similar to the odor of rotten eggs. Hydrogen sulfide is irritating and asphyxiating, and acute hydrogen sulfide poisoning generally has a very rapid onset, with damage to the brain or respiratory system, and can also be accompanied by dysfunction of substantial organs of the heart. Patients show different symptoms due to different concentrations of exposure. Mild hydrogen sulfide poisoning may manifest as lacrimation, stinging eyes, runny nose, burning sensation in the throat, or symptoms such as headache, weakness, dizziness, and nausea. Moderate poisoning is usually caused by exposure to high concentrations of hydrogen sulfide and is mainly characterized by neurological symptoms, including headache, dizziness, agitation, irritability, confusion or babbling, electric shock-like convulsions, generalized tonic spasms, and sudden coma, causing cardiac and respiratory arrest. In severe poisoning, the patient may be exposed to very high concentrations of hydrogen sulfide and may die of electric shock.