Which of the following gases is considered flammable or explosive in sewers?

Hydrogen sulfide (H₂S) is considered flammable and can be explosive in sewers because it is a colorless gas with a characteristic foul odor, reminiscent of rotten eggs. When hydrogen sulfide concentrations reach certain levels, particularly in confined spaces like sewers, it can form explosive mixtures with air. Additionally, H₂S poses significant health risks and can be lethal in high concentrations, further underscoring the importance of monitoring and controlling this gas in wastewater environments.

In sewers, organic matter decomposes anaerobically, producing hydrogen sulfide as a byproduct. The conditions in sewers can lead to the accumulation of H₂S, making it crucial for wastewater operators to be aware of its potential dangers, including its explosive characteristics when mixed with air at specific concentrations.

Understanding the properties of hydrogen sulfide is essential for safety protocols in wastewater treatment facilities, as this gas not only presents an explosion risk but also toxic hazards that can affect worker safety and health.