Neutron exposure at civil flight levels

Neutrons contribute to the exposure level at subsonic flight altitudes roughly by one half. The data on their spectrum differ rather substantially. A useful tool to improve the interpretation represents a calibration in properly formed reference fields. Another possibility is to compare the results with the reading of a reference instrument. Both approaches, together with analysis of available spectral data are presented in this contribution, an estimation of neutron exposure of aircrews at civil flight levels is given.