How to Wear a Personal Dosimeter Correctly

How to Wear a Personal Dosimeter Correctly

A personal dosimeter is one of the most important monitoring tools for occupationally exposed workers. Its role is to provide information about the exposure received during work, so that doses can be followed, reviewed, and kept under control.

However, a dosimeter is useful only if it is used correctly. A dosimeter worn incorrectly, left in a drawer, forgotten in the exposure room, or shared with a colleague may produce results that no longer reflect the real exposure of the monitored worker.

Romanian individual dosimetry regulations establish requirements for assessing occupational exposure to ionizing radiation, the responsibilities of the undertaking and individual dosimetry services, and the use of CNCAN-designated services for monitoring occupationally exposed workers.

What is a personal dosimeter?

A personal dosimeter is a device used to monitor individual exposure to ionizing radiation. It is assigned to one person and worn during the established monitoring period.

Depending on the activity and radiological risk, several types of dosimeters may be used:

• whole-body dosimeter — Hp(10);
• eye lens dosimeter — Hp(3);
• extremity dosimeter — Hp(0.07);
• other monitoring systems, where required by the activity.

A dosimeter is not protective equipment. It does not reduce dose; it monitors dose. Exposure reduction comes from work organization, application of ALARA principles, reducing time, increasing distance, and using appropriate shielding.

The dosimeter must be assigned to one person

One of the most important rules is that the dosimeter is personal. It belongs to one individual and is linked to that person’s dosimetric history.

The dosimeter must not be:

• shared with colleagues;
• exchanged between workers;
• worn by another person;
• used to monitor a room or equipment;
• placed near a radiation source for “testing”.

If a dosimeter is worn by someone else, the result can no longer be correctly interpreted. A high value may be assigned to the wrong worker, and the dosimetric history becomes unclear.

During an inspection or investigation of an unusual dose, traceability is essential. It must be clear who wore the dosimeter, during which period and under what conditions.

Where is the whole-body dosimeter worn?

The whole-body dosimeter is used to assess deep dose, associated with Hp(10). It is generally worn on the torso, in a position representative of the worker’s exposure.

In medical activities, the exact position may depend on the type of procedure, the use of personal protective equipment, and the instructions established by the dosimetry service, radiation protection expert, or internal procedure.

General rules:

• wear the dosimeter during work involving exposure risk;
• attach it visibly and securely;
• do not keep it in a trouser pocket or bag;
• do not leave it in the changing room or car;
• do not wear it outside work unless occupational exposure may occur;
• do not store it in the exposure room.

If a protective apron is used, the dosimeter position must be clearly established by procedure, because interpretation of the result depends on where it was worn.

How is the eye lens dosimeter worn?

The eye lens dosimeter is used to assess dose to the lens of the eye, associated with Hp(3). It may be required in activities where the eyes can receive significant exposure, such as certain interventional procedures or other activities with exposure close to the source or scattered radiation.

The eye lens dosimeter should be worn near the head, in a position representative of eye exposure, according to the instructions provided.

It is important that it:

• is not confused with the whole-body dosimeter;
• is worn by the person to whom it was assigned;
• is positioned consistently;
• is not left on a table, in a drawer, or in the exposure room;
• is returned on time for reading.

In practice, eye lens monitoring is relevant only if the dosimeter is worn correctly and consistently during the activities for which it was recommended.

How is the extremity dosimeter worn?

The extremity dosimeter is used to assess dose to the hands, fingers, or skin, associated with Hp(0.07). It is important in activities where the hands may be close to the source or in radiation fields relevant for extremities.

Depending on the dosimeter type, it may be worn as a ring, bracelet, or another dedicated system.

General rules:

• wear it on the hand indicated by the procedure;
• position it according to the instructions received;
• use it during the activities for which it was recommended;
• do not exchange it with colleagues;
• do not store it near sources;
• return it on time.

In nuclear medicine, interventional radiology, laboratories, or other activities where the hands are close to sources, extremity dosimeter positioning can significantly influence interpretation of the result.

What are the most common mistakes?

The most frequent mistakes are simple, but they can seriously affect monitoring results.

Examples include:

• the dosimeter is forgotten in the exposure room;
• the dosimeter is left on the equipment;
• the dosimeter is stored near radioactive sources or radiological installations;
• the dosimeter is worn by another person;
• the dosimeter is worn only occasionally;
• the dosimeter is returned late;
• the dosimeter is accidentally washed with clothing;
• the dosimeter is mechanically damaged;
• the dosimeter is intentionally exposed for “testing”;
• the worker forgets to report loss or damage.

These situations may lead to results that are difficult to interpret, the need for an investigation, or the assignment of an estimated dose.

Where should the dosimeter be stored when not worn?

When not being worn, the dosimeter should be stored in a designated place, away from radiation sources, extreme temperatures, excessive humidity, or mechanical damage.

The dosimeter should not be stored:

• in the exposure room;
• near radiological equipment;
• near radioactive sources;
• in a car;
• in clothing that may be washed;
• in places accessible to other people;
• together with other dosimeters if there is a risk of confusion.

The facility should have a clearly defined storage area, and staff should be trained to follow the same rule every time.

What happens if the dosimeter is lost or damaged?

Loss, theft, damage, or inability to use a dosimeter must be reported immediately. The situation must be documented, and the worker’s dose must be evaluated according to applicable procedures.

Individual dosimetry regulations establish responsibilities for occupational exposure assessment and dose recording, including situations where routine monitoring cannot be used normally.

In such cases, the following may be reviewed:

• the activity performed during the period;
• the worker’s dosimetric history;
• doses received by colleagues with similar activity;
• working conditions;
• any unusual events;
• available workplace monitoring data;
• the facility’s internal procedures.

The important point is that the situation must not be ignored. A missing dosimetric result must be explained and documented.

What should be done when an unusual value appears?

An unusual dosimetric value should not automatically be interpreted as a real dose, but it should not be ignored either.

The following should be reviewed:

• whether the dosimeter was worn correctly;
• whether it was stored properly;
• whether the dosimeter may have been accidentally exposed;
• whether the worker performed different procedures than usual;
• whether the working method changed;
• whether similar values appeared for colleagues;
• whether additional radiation protection measures are needed.

The result must be correlated with the real activity. The purpose of the investigation is not to assign blame, but to determine whether there was a use issue, a change in activity, or a real occupational exposure that requires action.

Who should explain how the dosimeter is worn?

The employer, RPO, radiation protection expert, and dosimetry service have different roles in organizing monitoring. In practice, personnel must receive clear, simple, and documented instructions.

Each monitored worker should know:

• which dosimeter was assigned to them;
• where it must be worn;
• when it must be worn;
• where it is stored;
• what must not be done with it;
• when it must be returned;
• what to do if it is lost;
• whom to notify if a problem occurs.

CNCAN states that designated dosimetry bodies have obligations regarding communication of routine dose assessment results to the employer and CNCAN, and individual dosimetry services must be designated according to applicable requirements.

Quick checklist for correct dosimeter use

Before work:

• check that you are wearing your own dosimeter;
• check that it is positioned correctly;
• do not cover, modify, or damage it;
• do not share it;
• do not leave it in the exposure room;
• wear it during activities involving exposure risk;
• store it only in the designated place;
• return it on time;
• report loss or damage immediately;
• ask the RPO if you are unsure where it should be worn.

How can Q RAD Laboratory help?

Q RAD Laboratory provides dosimetric monitoring services for occupationally exposed workers and supports the correct organization of individual dosimetry.

We can help with:

• supplying personal dosimeters;
• monitoring for whole body, eye lens, and extremities;
• establishing the required types of dosimeters;
• instructions for wearing and storing dosimeters;
• managing monitoring periods;
• issuing dosimetric reports;
• supporting the review of unusual values;
• records and documentation support;
• preparation for CNCAN inspections;
• guidance on radiation protection organization.

Through its own resources and authorized strategic partners, Q RAD can support organizations that want to maintain clear, traceable, and compliant dosimetric monitoring.

Conclusion

A personal dosimeter is useful only if it is worn and managed correctly. It must not be shared, forgotten, stored near sources, or used only occasionally. Each dosimeter must be linked to one person, one monitoring period, and real work activity.

Well-organized dosimetric monitoring helps the employer, the RPO, and the occupationally exposed worker understand exposure and take action when unusual situations occur.

Q RAD Laboratory can support your organization in implementing correct, clear, and easy-to-manage dosimetric monitoring.

This article provides general information. The exact way a dosimeter should be worn must be established according to the type of practice, risk assessment, internal procedures, recommendations of the radiation protection expert, and instructions of the dosimetry service.