At what exposure level can hydrogen sulfide be fatal?

Hydrogen sulfide (H2S) is a highly toxic gas that can be fatal at certain exposure levels. The correct answer, which indicates that an exposure level of 300 ppm (parts per million) can be fatal, reflects the recognized danger associated with inhaling high concentrations of this gas.

At approximately 300 ppm, individuals can experience severe respiratory distress, leading to a loss of consciousness and death if exposure is prolonged. The gas acts quickly by paralyzing the respiratory system, and even short durations can be life-threatening under these conditions.

Exposures to lower concentrations can also result in significant health effects, such as nausea and irritation of the eyes and respiratory tract; however, it is the 300 ppm level that is particularly noted for its acute toxicity and higher risk of fatality. As such, understanding these thresholds is crucial for safety in environments where hydrogen sulfide may be present, particularly in waste treatment operations, oil refining, and in sewers.