ISO 20785-3:2023

Overview

ISO 20785-3:2023 - "Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 3: Measurements at aviation altitudes" provides the technical basis for measuring ambient dose equivalent (H(10)) at flight altitudes*. The standard supports evaluation of cosmic radiation exposure to aircraft crew and validation of dose-calculation models by defining measurement principles, instrument characterization, correction factors and uncertainty treatment for in‑flight dosimetry.

Key topics and requirements

• Scope and quantities: Defines terminology and units consistent with ISO/IEC 80000-10 and specifies the operational quantity ambient dose equivalent (H(10))* as the measurable proxy for effective dose at altitude.
• Radiation field description: Summarizes the complex atmospheric and secondary radiation components encountered at aviation altitudes and includes representative particle fluence energy distributions (informative Annex A) for different solar and geomagnetic conditions.
• Measurement considerations:
  • Selection and characterization of instruments (active and passive) and requirements for calibration and traceability to national standards.
  • In‑aircraft measurement practices, including placement, background subtraction and application of correction factors for aircraft shielding and geometry.
  • Environmental and influence quantities: barometric altitude, geographic coordinates, solar activity, cabin pressure, temperature and humidity.
• Practical constraints for instruments:
  • Active detectors: power supply, vibrations/shock resilience, electromagnetic interference.
  • Passive dosimeters: handling of security X‑ray scanning and background subtraction.
• Safety, regulatory and quality: Addresses safety/regulatory requirements for in‑flight measurements and recommends procedures for uncertainty evaluation following ISO/IEC Guide 98 series (GUM).

Applications and users

ISO 20785-3:2023 is intended for:

• Primary and secondary calibration laboratories performing traceable calibrations for airborne dosimetry.
• Radiation protection authorities and governmental agencies implementing regulatory monitoring and compliance (e.g., occupational exposure frameworks, crew dose limits).
• Airlines, crew managers and occupational health specialists assessing and managing aircraft crew exposure, scheduling and pregnancy protection.
• Researchers and vendors developing, testing and validating in‑flight dosimeters and dose-calculation software.

Practical uses include validating calculated ambient dose equivalent maps, routine or campaign in‑flight surveys, instrument performance characterization, and demonstrating compliance with occupational dose guidance (e.g., EU Basic Safety Standards).

Related standards

• Other parts of the ISO 20785 series (see ISO website for the full list).
• ISO/IEC Guide 98-1 and 98-3 (uncertainty of measurement) and ISO/IEC 80000-10 (quantities and units).
• Referenced ICRP and ICRU guidance for dose assessment and operational quantities (as cited in the standard).

Keywords: ISO 20785-3:2023, cosmic radiation, aviation altitudes, ambient dose equivalent, dosimetry, in‑flight measurements, aircraft crew radiation, calibration, uncertainty, radiation protection.