ISO 11665-7:2012

Overview

ISO 11665-7:2012 - Measurement of radioactivity in the environment - Air: radon‑222 - Part 7: Accumulation method for estimating surface exhalation rate describes a practical, short‑term technique to estimate the radon-222 surface exhalation rate at the interface between a medium (soil, rock, laid building material, walls, etc.) and the atmosphere. The method is based on accumulating radon in a sealed container of known effective volume for a known accumulation duration (typically a few hours), sampling the container air, measuring the radon activity concentration and calculating the exhalation flux. The standard is explicitly estimative and intended for site investigations, source searches or comparative studies rather than absolute flux certification. It does not cover device calibration conditions.

Key technical topics and requirements

• Principle: Accumulate radon in an accumulation container and derive surface exhalation rate from the measured concentration increase over time.
• Applicable range: Method is applicable for exhalation rates greater than about 5 mBq/m2/s.
• Accumulation container:
  • Known geometric characteristics (effective surface and effective volume).
  • Effective volume ≥ 10 × sampled air volume.
  • Materials must resist radon diffusion and not promote heating under sunlight.
  • One or more orifices with closing systems for sampling.
• Sampling and detection:
  • Sampling characteristics and duration chosen to represent container atmosphere.
  • Compatible radon detection methods (continuous or spot) as referenced in annexes.
• Influence quantities: Leakage, back diffusion, decay, and environmental factors (temperature, humidity, precipitation, snow cover) must be considered.
• Data treatment:
  • Models account for decay and loss; for negligible leakage an initial linear increase approximation is used (C(t) ≈ φ·S/V · t).
  • Results require expression of standard uncertainty, decision threshold, detection limit and confidence intervals.
• Reporting: Test report elements and example result sheets are provided in the standard.

Practical applications and users

• Useful for environmental scientists, radiation protection professionals, geologists, radon surveyors, building inspectors, and regulatory authorities conducting:
  • Site investigations and mapping of radon exhalation hot spots.
  • Comparative studies of exhalation rates at the same site over time.
  • Source localization (e.g., uranium-bearing soils, contaminated building materials).
• Not intended for laboratory calibration of instruments; best used for short‑term in‑field assessments under documented environmental conditions.

Related standards

• ISO 11665-1, -5, -6 (background, continuous and spot activity concentration methods)
• ISO/IEC 17025 (laboratory competence)
• IEC 61577-1 (radon measuring instrument principles)

Keywords: ISO 11665-7:2012, radon-222, surface exhalation rate, accumulation method, radon measurement, environmental radioactivity, accumulation container, back diffusion, leakage, sampling, uncertainty.