Model RnCAM


  • Dynamic Range: 0.1 to 2,000 pCi/L
  • Sensitivity: 0.65 CPM per pCi/L
  • Rugged weatherproof housing design suitable for outdoor use
  • Detects radon-220 and radon-222 alpha
  • Full temperature compensation from -20 °C to +50 °C
  • RS-232 output (LAN optional)
  • Microprocessor controlled electronics with non-volatile memory


The Overhoff RnCAM is a hand-held portable instrument that measures airborne radon-222 and radon-220 over a wide range of concentrations with a very fast response time and excellent sensitivity.  This radon monitor is useful to those individuals who need to quickly establish radon background levels, demonstrate compliance with local regulations, or for radon mitigation efforts.  A large 300cc ionization chamber detector is used to measure below the US EPA’s recommended radon mitigation limit of 4 pCi/L in as little as a few minutes.

This instrument runs on an internal Li-ion battery or AC power.  To save power, the internal pump is set to cycle through an on-off cycle – the default is 5 seconds on and 55 seconds off . When the monitor counts a selectable number of radon decay events (the default is 50), the monitor will calculate the radon concentration in pCi/L, Bq/m3, or kBq/m3, based on the time required to count that number of decays.  The monitor has an audio alarm which will sound due to an overlimit condition.  On an alarm condition, a set of contacts will also close to activate an external alarm annunciator or other relay.  The alarm limit value can be set using front panel button “C” – pressing the button allows you to choose a limit value from one of four preset values (these preset values can be changed using the software).

The RnCAM contains a microprocessor, which counts decay events, calculates the concentration, stores the concentration values in its flash (non-volatile) memory, displays the value on the LCD screen, and can transfer data to a host computer.  Communication to a host computer is RS-232 (through a standard USB-to-RS232 converter if necessary).  Configuration software running on the PC permits configuration and calibration.

Logs 40,000 data points to accurately establish the daily variation in radon concentrations.  The radon monitor’s internal rechargeable battery can operate the monitor for 24 hours.  By using the AC/DC adapter, the monitoring time can be extended indefinitely which allows for logging the variations in radon concentrations due to the environmental effects of changes in barometric pressure and rainfall.

Overhoff’s radon monitor is extremely fast, accurate, and reliable.  The real-time measurement is especially useful for alerting personnel when radon levels rise or build up and for radon mitigation efforts.  An upgraded alarm relay can be included to turn on radon mitigation ventilation systems when the alarm has exceeded the set-point.  Mitigation of radon concentrations can be as simple as a change in ventilation flow or a more complex effort such as installing a vapor barrier.

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