Radon monitor. (home-built environmental radon gas detector)

Build this radon monitor to detect a possible health threat in your home and, while doing it, learn more about radioactivity.

THIS TWO-PART ARTICLE DISCUSSES the design, construction, and use of a simple, inexpensive environmental radon gas detector that you can build. It is called the beverage can environmental radon monitor or BERM because its ionization chamber sensor is made from a readily available aluminum beverage can. You will be given a choice of methods for measuring and recording events or rates that can be translated into units of radon density.

Most people are exposed to environmental radon in excess of the natural rate because of the time they spend indoors. This first article explains what radon is, why it is a health hazard, and the importance of knowing the level of radon in the rooms of your house where you spend most of your time while indoors. It also includes the information needed to build the ionization chamber, its amplifier circuitry, and alternative circuits for charging the chamber's internal high-voltage capacitor to 500 volts.

The second part of this article covers pulse-rate measurement, instrument calibration, and the conversion of pulse rates to radon density units. The article also offers alternative methods and circuits for performing these functions.

Even if the BERM is only crudely calibrated, it can warn you of unsafe radon levels in your home. However, when properly calibrated, it can give readings that compare favorably with these obtained from professional radon monitoring instruments costing thousands of dollars. Constructing the BERM will give you "hands on" experience in measuring a common form of radioactivity, and give you a better understanding of how it produces isotopes, subjects not easily grasped in lectures or from reading.

The cost of parts to build the BERM, exclusive of a power supply, is typically less than $20. Because most of the components are readily available, you might be able to reduce even that modest cost by making use of parts you already have on hand. You will need the standard electronic technician's set of hand tools as well as such basic electronic test equipment as a two-channel oscilloscope and either an analog or digital multimeter.

What is radon?