Civil Defense Geiger Counters - Ion-chamber Survey Meters

Ion-chamber Survey Meters

These are instruments using the ionisation chamber principle.

If the meter on any of the ion chamber devices are observed to respond at all to a radiation source, evacuation of the area should be considered. No legally exempt source of gamma radiation would be expected to cause any visible deflection of the meter on its most sensitive setting, so it might be assumed that such a radiation field could be dangerous. Such a meter would not be expected to detect the presence of radiation except the very high levels that might be found in the event of a nuclear weapon detonation or a major release of radioactive material as from a nuclear reactor meltdown. It should be noted that the CD V ion chamber units are now all approaching 50 years old at a minimum and that they contain parts that are sensitive to moisture, so relatively frequent calibration and inspection by an accredited and properly equipped facility is required to ensure reliable and accurate function. There are no means by which an individual, even an advanced amateur, can calibrate these units as it requires a very intense and highly regulated radiation source to do so.