Apparatus and method for measuring radon

An apparatus configured to measure decay(s) from Radon progeny, the apparatus comprising:

• an air moving device configured to create an airflow;
• a filter;
• a pathway configured to guide the airflow through the filter, wherein the filter is configured to collect at least part of the Radon progeny in the airflow;
• a semiconductor detector configured to detect alpha radiation from the Radon progeny collected by the filter, the semiconductor detector being configured to spectrally resolve the alpha radiation and output a detector signal indicative of two or more respective energy levels of the detected alpha radiation;
• wherein the apparatus comprises or is connectable to electronic circuitry configured to interpret the detected alpha radiation to thereby perform a Radon measurement;
• wherein the apparatus comprises or is connectable to an output device configured to output an equivalent equilibrium Radon concentration and/or to output a Radon concentration;
• and
• wherein the semiconductor detector has an active area less than 225 mm2, wherein the filter is supported by a filter holder, and wherein the filter holder is fixedly positionable in the apparatus.