Which device detects the trace gas at the leak?

• A. Ultrasonic Leak Detector
• B. Microfoam Solution
• C. Trace Gas and Electronic Leak Detector
• D. Electronic Leak Detector

Answer: (D)

The ability to detect a leak at the trace level comes from using a sensor that responds to very small concentrations of a tracer gas. An electronic leak detector is designed for this purpose—it senses the presence of the gas in the area around the leak and provides an alert to pinpoint the leak location. This direct gas-detection capability is what makes it the best choice for tracking trace gas.

Ultrasonic leak detectors, while useful in some scenarios, rely on listening for the sound of escaping gas rather than measuring its concentration, so they can miss quiet leaks or leaks in noisy environments. The microfoam solution gives a visual indication by bubbles where a leak is sprayed, but it requires access to the leak area and isn’t a true trace-gas measurement tool. The phrase “trace gas and electronic leak detector” could describe the idea, but the instrument that directly detects the trace gas and guides location is the electronic leak detector, making it the most appropriate answer.