As a kind of radioactive noble gas, radon is widely found in soil, rock, water and air. Long-term exposure to excessive radon gas will jeopardize human health, and radon measuring instrument has thus become a key equipment for monitoring radon concentration and safeguarding the safety of living and working environment. Its working principle is mainly based on the following common techniques.

Electrostatic collection method: Utilizing the electrically charged characteristics of radon and its daughters. The daughter particles produced by the decay of radon gas carry an electric charge. A strong electric field is set up inside the measuring instrument, and under the action of the electric field, the charged radon daughters are collected on a specific electrode. By accurately measuring the collected charge, the radon concentration in the environment can be calculated based on the correspondence between the charge and the radon concentration. This method is more sensitive and capable of detecting low concentration of radon gas, and is commonly used for accurate measurement of radon concentration in indoor environment.

Scintillator bottle method: The core of this method lies in the scintillator material. When the α particles generated from the decay of radon and its daughters hit the scintillator inside the scintillator bottle, the scintillator will be excited and emit weak flashes of light. These flashes are captured by a photomultiplier tube, which amplifies the light signal and converts it into an electrical pulse signal. The measuring instrument analyzes and counts the number and intensity of the electric pulses to derive the radon concentration value. The scintillation bottle method is relatively easy to operate and can realize rapid measurement, which is widely used in some emergency testing or large area preliminary screening scenarios.

Activated carbon adsorption method: Activated carbon has strong adsorption ability and can adsorb radon gas in the air in large quantities. The measuring instrument places the activated carbon in a specific sampling device, and after a period of adsorption, the radon concentration in the environment can be deduced by measuring the intensity of gamma rays generated by the decay of radon gas adsorbed by the activated carbon, and according to the pre-established calibration curve between the intensity of gamma rays and the radon concentration. This method is applicable to cumulative measurements over a long period of time and can reflect the average radon concentration level over a period of time, and is commonly used for assessing the risk of radon exposure in long-term residential environments.

By virtue of these principles, radon measuring instruments play an important role in various types of environmental radon monitoring, providing powerful support for people to understand the radon pollution situation in a timely manner and take effective protective measures.