The purpose of designated areas is to help manage the radiation risk and to control the extent of radiation exposure. Under IRR17, Regulation 17, the designation of areas is a legal requirement and the responsibility of the employer in conjunction with the RPA.
There are two legally defined types of designated areas:
Controlled Area
A controlled area is defined as an area where:
- it is necessary to follow special procedures designed to restrict significant exposure
- any person working in the area is likely to receive:
- an effective dose greater than 6 mSv a year or
- an equivalent dose greater than 15 mSv a year for the lens of the eye
- an equivalent dose greater than 150 mSv a year for the skin or the extremities
- there is a significant risk of spread of contamination (not applicable with x-ray)
Supervised Area
Supervised areas are designated where:
- it is necessary to keep the conditions of the area under review to determine whether a controlled area is needed.
- workers are likely to receive an effective yearly dose > 1 mSv.
- workers are likely to receive an equivalent dose greater than 5 mSv a year for the lens of the eye.
- workers are likely to receive an equivalent dose greater than 50 mSv a year for the skin or the extremities.
In veterinary x-ray imaging situations, areas are designated as controlled areas; it is rarely necessary, if ever, to designate a supervised area.
Where a controlled area has been designated, the employer must make and set down in writing local rules which adequately describe the extent of the controlled area and are appropriate to the radiation risk and the nature of the work undertaken. In addition, the employer must ensure that the controlled area:
- is physically demarcated or delineated by some other suitable means
- has suitable and sufficient warning signs
Warning Signs
Appropriate warning signs need to be placed at the edge of any designated controlled area. Suitable signage should state the nature of the source of ionising radiation, for example ‘X-ray’. The risk that source poses, for example ‘external exposure’. There should be a trefoil symbol, the designation, for example ‘controlled area’, and any specific requirements, ‘no unauthorised entry’ for example.
Warning Lights
In veterinary practices warning lights are required to be failsafe where reasonably practicable. Failsafe lighting is a system where if the light fails to illuminate, it’s not possible to make any other exposures with your x-ray units until the light is fixed or the lightbulb replaced.
It is the opinion of the HSE that it should be reasonably practicable to comply with this requirement and it should not involve replacing existing radiographic equipment.
Off-Site Imaging
For off-site equine radiography additional considerations are required; a temporary controlled area must be designated and a dynamic risk assessment conducted prior to imaging commencing.
The temporary controlled area must include:
- Clear physical demarcation through the use of barriers, cones, tape etc
- Clear and appropriate warning signage
- The operator must have full visibility of the controlled area
- The operator must restrict unauthorised access to the controlled area and must terminate the exposure immediately if there is any breach of the controlled area
The designation of areas is one of the elements of radiation protection that the employer should consult an RPA on. SGA can provide advice to veterinary practices, see our website for further details.
If you are considering opening a new veterinary practice and installing x-ray equipment, then enrol on our Online Learning Platform, where you’ll find a handy guide which will take you through each step of the process, from concept to first clinical use.
