Module 6 - Radiation Dosimetry

Dosimeter with holder

Extremity Dosimeter

(Extremity Dosimeter)

At the University of Washington, radiation dosimetry is provided to monitor occupational radiation exposure for those workers who use radiation sources under certain conditions.  University of Washington dosimeters should not be used to measure occupational doses received at any other institution or to measure doses from non-occupational sources such as medical x-rays.


State and federal regulations require that those persons who are likely to receive 10% or more of the annual radiation dose limits must be provided with radiation dosimetry.  This means that federal and state regulations require monitoring for any person likely to receive a whole body dose of 500 mrem or more or a skin or hand dose of 5000 millirem or more. 

Under University of Washington requirements, you must wear dosimetry if:

  • You operate x-ray machines (including open x-ray diffraction equipment)
  • You are a Declared Pregnant Worker working in a lab where x-ray and gamma emitters or energetic beta emitters are used
  • If you use open sources of radioactive materials under certain conditions
  • If you use sealed sources under the following conditions:
Sealed Sources
Na-22, Co-60, Cs-137 and Ra-226
and other energetic beta/gamma emitters 
 Used in amounts 10.0 mCi

More Information about Dosimeters

The University of Washington Radiation Safety Manual contains additional information on dosimeters.


Dosimetry is not routinely provided to workers who do not meet the criteria described in the Required Dosimetry section.

If you have concerns about your radiation exposure and would like to be monitored even though you do not meet the Required Dosimetry criteria, you may either contact Radiation Safety directly or you may ask your Authorized User or your lab manager to request dosimetry for you.  If you request dosimetry even though you do not meet the Required Dosimetry criteria, dosimetry will be provided for you for a year.  After the first year of monitoring, Radiation Safety will review your dose history and determine whether dosimetry should be continued.


In 2002 the University implemented a Dosimetry Policy to curtail the number of unreturned and missing dosimeters University of Washington Unreturned Dosimeter Policy  Prior to the implementation of the current dosimetry criteria and over the last 25 years, the University of Washington provided radiation dosimeters to many more workers than is required.  In 2002, the University of Washington provided dosimeters to  about 1400 people per year.  Approximately 90%+ of all monitored persons received no measurable dose. 

During this period of time, no one using sealed sources received a dose high enough to require monitoring under federal regulations.


This is the end the Dosimetry Module, which is the sixth of the seven Sealed Source Radiation Basics modules.  The next module is the Using  Sealed Sources Safely Module.

Working Safely With Sealed Sources (Module #7)

Return to the Sealed Source Training Introduction Page