Massachusetts Wastewater Practice Exam

Explosive gases may be detected using which devices?

1. Thermometers.

2. LEL meters.

3. Pressure gauges.

4. Smoke detectors.

The correct answer is: LEL meters.

LEL meters, or Lower Explosive Limit meters, are designed specifically to measure the concentration of flammable gases in the air. They provide critical safety information by indicating whether the levels of explosive gases are within a range that poses a risk of ignition. The LEL is the lowest concentration of gas in the air that can ignite; thus, LEL meters are essential tools in wastewater treatment plants and other environments where explosive gases, such as methane or hydrogen sulfide, may be present. These meters continuously monitor air quality and ensure that workers can operate safely without exposure to hazardous conditions. In contrast, thermometers measure temperature, which does not provide information about gas concentrations. Pressure gauges measure the pressure within a system, and while important for overall system monitoring, they do not detect the presence of explosive gases. Smoke detectors are designed to identify smoke particles from combustion and alert users about fire, but they do not specifically measure gas concentrations. Therefore, LEL meters are the appropriate devices for detecting explosive gases.