Revised on
01/26/17 02:18pm
SafetyNet #

How to Monitor Your Lab for Radioactive Contamination

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As a condition of your Radiation Use Authorization (RUA), you must maintain an ongoing radiation monitoring program for all radionuclide work areas, storage locations, and equipment that may have come into contact with radioactive materials.


  • Perform monitoring immediately after using radioactive materials. If work has been performed with anything except H-3 (tritium), a GM survey meter with a pancake probe can be used to detect low levels of beta or gamma emitters.
  • Wipe test results must be recorded in a logbook a minimum of once every two weeks if routine work has occurred. If work with radioactive materials is infrequent, wipe tests should be performed after each use.
  • More frequent monitoring may be required depending on the experimental protocol. This will be specified in the conditions of your RUA.


  • A detailed floor plan of the laboratory should be drawn up to include all radionuclide work areas, storage locations, and equipment used.
  • The floor plan should be copied, dated, and the wipe locations identified on the map. The results should be attached to the map along with an indication of which wipe test was used for the background count. The background serves as a reference for monitoring and an integrity check on all machines with internal standards.
    Note: Wipe tests should cover approximately 100 cm2 (i.e., 4" x 4").


  • Areas that exceed the following guidelines are to be considered contaminated.

Restricted Area Type

Alpha Emitter (cpm/100 cm2)

Beta, Gamma Emitter (cpm/100 cm2)

Controlled Area

18 counts above background

60 counts above background

Small Contamination Control Zone and Large Contamination Control Zone

88 counts above background

300 counts above background

Small Contamination Control Zone within a Large Contamination Control Zone

176 counts above background

600 counts above background

Please refer to Part V D in the Radiation Safety Manual for further definitions of the specific areas.

  • Decontaminate the area(s) until the level of contamination is below the above guidelines. Attach the results of the decontamination (i.e., first attempt, second attempt, etc.) to the original results and laboratory map. If you are unable to decontaminate down to acceptable levels, call the Office of Environmental Health and Safety at (530) 752-1493 or UC Davis Health (UCDH) Health Physics at (916) 734-3355 for further assistance.
  • Do not attempt decontamination in the case of a major spill (millicurie amounts). Control the area and call the Office of Environmental Health and Safety or UCDH Health Physics. If after normal hours, call 9-1-1 or the Hospital Operator.

Additional References
See SafetyNet #37, “Radioactive Spills, Splashes, and Decontamination” for more information.