As a user of radioactive materials, you should routinely monitor your laboratory for contamination. This article will discuss the capabilities and limitations of the survey meters in your laboratory. Beta particles must have sufficient kinetic energy to pass through the detector window and into the gas filled sensitive volume of the detector. GM detectors are comparatively poor at detecting radioisotopes that emit only photon radiation. Since the probability of a photon interaction occurring in dense matter is significantly greater than in a gas filled detector, the detection of photon emitting radioisotopes is best accomplished by using a scintillation type detector.
All survey meters have a background reading.
Background is what a clean meter reads when it is outside the laboratory. The sources of radiation detected as background are from terrestrial sources, building materials and cosmic rays. For a GM detector, this usually fluctuates between 10 and 100 counts per minute. The radiation user should note the normal background readings in their building. A radiation detector should not have a sustained, elevated background reading.