What Is a Dosimeter
A dosimeter is a personal monitoring device that measures cumulative exposure to ionizing radiation. Workers in nuclear facilities, medical imaging departments, dental offices, and industrial radiography wear dosimeters to track their radiation dose over time. The most common type is the film badge or electronic personal dosimeter (EPD), clipped to clothing at chest level.
OSHA Requirements and Regulations
OSHA requires dosimetry monitoring for any worker who receives more than 10% of the annual occupational dose limit, which is 5,000 millirems (50 millisieverts) per year. Employers must provide dosimeters at no cost to employees and maintain records for 30 years after employment ends. Monitoring must occur at least quarterly, with monthly or weekly intervals for higher-exposure roles.
Radiation safety audits, a standard part of OSHA compliance, include verification that dosimeters are properly issued, worn, and processed. Missing or damaged dosimeters must be reported immediately and replaced.
How Dosimeters Work in Practice
- Film badges: Contain photographic film sensitive to radiation. Darkening indicates exposure level. Cost is typically $15 to $30 per badge and requires lab processing after each monitoring period.
- Electronic personal dosimeters: Provide real-time dose readings with alarm thresholds. Alert workers when approaching dose limits, supporting the ALARA principle of keeping doses as low as reasonably achievable.
- Ring dosimeters: Measure hand exposure for workers handling radioactive materials directly. Worn on the finger to track localized dose.
- Whole-body dosimeters: Standard issue for all radiation workers, positioned at torso level for accurate measurement of effective dose.
Practical Applications for Safety Managers
Safety managers must establish a dosimetry program that tracks exposure trends. If an employee's dose approaches 25% of the annual limit (1,250 millirems), workload should be reassessed to prevent exceeding exposure thresholds. Document all readings and investigate any anomalies. Regular dosimetry data review supports emergency preparedness by identifying which employees have ongoing radiation exposure and may need special consideration during incidents.
For homeowners, dosimeters are relevant if you work with radon mitigation, handle old radioactive sources, or live near industrial facilities. Home radon testing kits operate on similar principles and provide cumulative exposure data over weeks or months.
Common Questions
- How often should dosimeters be exchanged? Most employers use quarterly exchange cycles, though high-exposure roles may require monthly cycles. The dosimeter service provider supplies preaddressed envelopes for return and calibrated replacements.
- What if a dosimeter is lost or damaged? Report it immediately to your radiation safety officer. OSHA requires an incident report and estimation of potential exposure based on work performed during the period. This cannot be ignored or simply replaced without documentation.
- Can I reuse a dosimeter? No. Each dosimeter is calibrated for one monitoring period. Reuse invalidates the measurement and violates OSHA requirements.