What does PID stand for?

• A. Particle Ionization Device
• B. Photo Ionic Detector
• C. Photo Ionization Detector
• D. Photonic Ion Detector

Answer: (C)

The concept tested is how the acronym PID describes a specific type of detector that uses light to ionize molecules and then measures the resulting current. The best choice is Photo Ionization Detector because it correctly names the process: ions are produced by photons from a UV light source (photoionization), and the detector senses those ions to determine the presence and amount of volatile organic compounds. The other options misstate the mechanism or terminology—“Particle Ionization Device” would imply ionizing particles rather than molecules with light; “Photo Ionic Detector” uses the word ionic instead of ionization, which isn’t the standard term; and “Photonic Ion Detector” would suggest detecting photons or ions rather than using light to ionize target molecules. In practice, a PID is valued for its ability to detect VOCs at low concentrations by leveraging photoionization to create measurable ions.