At what concentration can hydrogen sulfide be fatal?

Hydrogen sulfide (H₂S) is a highly toxic gas that can be lethal at certain concentrations due to its ability to inhibit cellular respiration. At concentrations around 300 parts per million (ppm), exposure can lead to severe effects including rapid loss of consciousness and respiratory failure, resulting in death if not immediately treated.

At lower concentrations, effects may include irritation to the eyes, nose, and throat, along with headaches and dizziness. However, at 300 ppm and above, the gas can rapidly overwhelm the body's systems, causing symptoms to escalate quickly to the point of fatality. Understanding these concentration thresholds is critical for safety in environments where hydrogen sulfide exposure may occur, such as in certain industrial settings or when working with wastewater systems.