Tennessee Wastewater Operator Practice Exam

How can the presence of methane gas be detected?

1. By a flame detector

2. Using an LEL sensor set up for methane

3. Through visual inspection

4. With a colorimetric tube

The correct answer is: Using an LEL sensor set up for methane

The best method to detect methane gas is by using an LEL (Lower Explosive Limit) sensor set up specifically for methane. LEL sensors are designed to monitor the concentration of combustible gases in the atmosphere and will provide measurements indicating when methane levels approach a dangerous threshold. LEL sensors work by continuously sampling the air and using various technologies, such as catalytic beads or infrared sensors, to detect the presence of methane and other combustible gases. These sensors are specifically calibrated to alert operators when concentrations reach predetermined levels, allowing for appropriate safety measures to be enacted in environments where methane may be present, such as wastewater treatment facilities. While flame detectors can be effective for detecting flames or heat from combustion, they do not specifically measure gas concentrations and would not reliably indicate the presence of methane without associated combustion. Visual inspection can identify potential leaks or issues indirectly but lacks specificity and can't quantify the presence of methane gas. Colorimetric tubes can be used to measure gas concentrations but are not as reliable or real-time as LEL sensors, which offer continuous monitoring and immediate feedback regarding gas levels.