Associate Safety Professional Practice Exam

What is the basic operating principle of a portable combustible gas meter?

1. Measurement of gas pressure

2. The impact of gas expansion

3. Electrical resistance change from gas combustion

4. Sound detection of gas leaks

The correct answer is: Electrical resistance change from gas combustion

The basic operating principle of a portable combustible gas meter relies on the electrical resistance change that occurs during gas combustion. When a combustible gas is present, it undergoes oxidation when it comes into contact with a sensor within the meter. This process generates heat, which alters the electrical resistance of the sensor material. By measuring these changes in resistance, the device can quantify the concentration of combustible gases in the air. This principle is vital for safety as it allows users to detect hazardous gas levels before they reach dangerous thresholds. Monitoring gas concentrations effectively helps prevent potential explosions or health issues from gas inhalation. Other options do not align with the fundamental operation of these meters. Gas pressure measurement typically relates to a different class of equipment designed to quantify pressures rather than concentrations. The impact of gas expansion might relate to thermodynamic principles, but it does not serve as a direct method for measuring gas presence in the way a combustible gas meter does. Sound detection of gas leaks approaches a different technique, where acoustic methods are utilized to identify leaks, which is not the primary function of a portable combustible gas meter.