Which of the following is NOT a type of CRM?

The correct answer pertains to the specific definition of Continuous Radon Measurement (CRM) devices. The Ionization Chamber is a type of device that is generally considered a "point" measurement device rather than a continuous monitoring system. While it can measure ionizing radiation and is often used for radon measurements, it operates differently from the continuous types of monitors listed in the other choices.

In contrast, the Scintillation Cell/Photo Multiplier Tube measures radon levels continuously by detecting the light produced when radon decays, making it suitable for CRM. The Pulsed Ion Chamber is designed for rapid detection of radon concentrations over a period of time. Solid State Silicon Detectors also provide continuous measurements, as they can monitor the decay events of radon over time with high sensitivity.

The ability of these devices to provide continuous data on radon concentrations distinguishes them from the Ionization Chamber, which does not fit this classification. Understanding these distinctions is key in the context of radon measurement technology and its practical application for environmental safety.