Personal dosimeters are worn by radiation workers to measure and record their occupational exposure to ionising radiation over a defined monitoring period. Dose records are used to demonstrate compliance with radiation safety requirements and to confirm that exposures remain as low as reasonably achievable.
To ensure dose records accurately reflect occupational exposure only, it is important to understand and manage non‑occupational sources of radiation. This is particularly important for workers who travel as part of their role.
Personal dosimeters and travel
Where possible, personal dosimeters should remain at the workplace and be stored with the control dosimeter. However, for workers who travel for work, this is not always practical.
When a personal dosimeter is taken away from the workplace, it may be exposed to sources of radiation that are unrelated to work activities. These exposures can contribute to the recorded dose and make interpretation of occupational exposure more difficult.
Non‑occupational contributors to dose during travel
Several factors can increase the dose recorded by a personal dosimeter during travel:
- Differences in natural background radiation, including variations in ground composition between locations.
- Increased cosmic radiation at altitude, particularly during domestic and international flights.
- Exposure from airport X‑ray baggage screening systems.
Where practicable, carrying a travel (control) dosimeter alongside the personal dosimeter allows these non‑occupational exposures to be identified and accounted for. If this is not possible, the most effective way to minimise non‑occupational dose is to prevent the personal dosimeter from being exposed to X‑ray baggage scanners.
X‑ray baggage scanners and dosimeter exposure
Personal dosimeters should not be placed through X‑ray baggage scanners. The radiation dose delivered by these systems varies depending on the scanner type and imaging modality.
Older flat‑panel X‑ray scanners generally deliver lower doses. Newer CT‑based baggage scanners, now commonly used for carry‑on baggage, can deliver substantially higher doses and may significantly affect dosimeter readings.
Typical dose levels from baggage screening systems are shown below:
| Style | Typical Dose |
|---|---|
| Carry on Baggage Flat panel scanner | 4.5-6.3 uSv |
| Carry on baggage CT scanner | 600 uSv |
| Oversize scanner | 3.4 uSv |
| Checked baggage scanner | 12 uSv |
Recommended practice when travelling
When travelling for work, workers should:
- Keep personal dosimeters on their person at all times.
- Do not place dosimeters in carry‑on or checked baggage.
- Request hand inspection of the dosimeter by aviation security staff instead of X‑ray screening.
- Be aware that aviation security staff may swab the dosimeter for security screening. Swabbing does not affect the performance or accuracy of the dosimeter.
Following these practices helps ensure recorded doses more accurately represent occupational exposure, supports reliable dose assessment, and assists with compliance with radiation safety requirements.
