Aircraft crew and frequent flyers are exposed to elevated levels of cosmic radiation of galactic and solar origin and secondary radiation produced in the atmosphere, the aircraft structure and its contents. Following recommendations from the International Commission on Radiological Protection (ICRP), the European Union introduced a revised Basic Safety Standards Directive which included exposure to natural sources of ionising radiation, including cosmic radiation, as occupational exposure.
Where the assessment of the occupational exposure of aircraft crew is necessary, the preferred approach to monitoring is by recording staff flying times and calculated route doses. However, there is a requirement to periodically validate calculations by measurement.
The then Radiation Protection Division of the Health Protection Agency (HPA) (now Public Health England) developed a passive survey instrument to make these measurements. In general, several return flights are required to make a measurement of acceptable precision.