The Design of Diagnostic Medical Facilities where ... - ResearchGate

Published occupancy factors, shown in Table 5.5, are intended to be indicative but provide useful guidance
where other data are not available (BIR, 2000, NCRP, 2004). There are some differences in the levels
recommended by the BIR and the NCRP, but they both follow a broadly similar approach. One exception is
the occupancy for employee lounges (NCRP)/staff rooms (BIR) which is recommended as 1/5 and 100%
respectively. The BIR suggest that the lowest occupancy factor used be 5% (BIR, 2000). An RPA should be
consulted regarding occupancy levels where additional guidance is required.
Particular care must be taken when classifying corridors as low occupancy areas. There may be another room
or office located across the corridor with a much higher occupancy and it must be ensured that such areas
are adequately protected. Likewise a low occupancy space outside a window may give a false sense of
security if there are nearby buildings with high occupancy. Adjacent offices/buildings that are not under the
same administration, or that are owned by a third party, should be assumed to have an occupancy factor of
100%, as they are subject to change without consultation or control (NCRP, 2004).
Finally, in this connection, shielding calculations must be reviewed if the use/occupancy of an adjoining area
changes. This is an issue over which there may be little control and which can inadvertently give rise to
unexpected radiation hazards. It is well to make allowances for this at the design stage as records of the
shielding calculations and specifications may not always be available or accessible in the future.
Table 5.5: Suggested occupancy factors for radiation shielding design (based on BIR, 2000 and NCRP, 2004)
Location BIR NCRP
Adjacent X‐ray room 100% 1
Reception areas 100% 1
Film reading area 100% 1
Offices, shops, living quarters, children’s indoor play areas,
occupied space in nearby buildings
100% 1
X‐ray control room 100% 1
Nurses’ station 100% 1
Staff room 100% 1/5
Patient examination and treatment rooms 50% 1/2
Wards, patient rooms 20% 1/5
Staff rest rooms - 1/5
Corridors 20% 1/5
Corridor doors - 1/8
Toilets or bathrooms 10% 1/20
Outdoor areas with seating 10% 1/20
Storage rooms 5% 1/20
Unattended vending areas 5% 1/20
Patient changing room 5% 1/20
Unattended waiting rooms 5% 1/20
Stairways 5% 1/40
Unattended car parks 5% 1/40
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