Which instrument uses ultraviolet ionization rather than color change to detect vapors?

Which instrument uses ultraviolet ionization rather than color change to detect vapors?

• A. General Area Sampling
• B. Colorimetric Tubes
• C. Photoionization Detectors (PIDs)
• D. PIDs

Answer: (C)

The test is about detection methods that rely on a mechanism other than a visible color change. A photoionization detector uses ultraviolet photons to ionize gas molecules; the resulting ions produce an electrical current that the instrument measures. The signal is proportional to vapor concentration, and no color change is involved. This is what sets it apart from colorimetric tubes, which detect vapors by a chemical reaction that changes color. General Area Sampling is a sampling approach, not a real-time detection method like a PID. The singular form “Photoionization Detectors” points to the same instrument type, but the essential idea is the ultraviolet photoionization mechanism itself.

The test is about detection methods that rely on a mechanism other than a visible color change. A photoionization detector uses ultraviolet photons to ionize gas molecules; the resulting ions produce an electrical current that the instrument measures. The signal is proportional to vapor concentration, and no color change is involved. This is what sets it apart from colorimetric tubes, which detect vapors by a chemical reaction that changes color. General Area Sampling is a sampling approach, not a real-time detection method like a PID. The singular form “Photoionization Detectors” points to the same instrument type, but the essential idea is the ultraviolet photoionization mechanism itself.