What technology does a Photoionization Detector (PID) use to measure gas concentration?

A Photoionization Detector (PID) utilizes ultraviolet (UV) light to measure the concentration of various gases. The device emits UV light into the air sample, which ionizes certain chemicals present in the gas. This ionization process produces charged particles, generating a measurable electrical current. The strength of this current correlates with the concentration of the gas, allowing the PID to quantify the presence of volatile organic compounds (VOCs) and other gases.

While other technologies such as infrared light, laser beams, and broad categories like electromagnetic radiation can be used for gas detection—each operates on different principles and targets various types of substances—the PID specifically relies on UV light for its ionization mechanism, making it the correct answer in this context.