Overview - EN ISO 11665-7:2015 / ISO 11665-7:2012 (radon-222 accumulation method)
EN ISO 11665-7:2015 (identical to ISO 11665-7:2012) provides guidelines for estimating the radon-222 surface exhalation rate using the accumulation method. The method measures radon activity that emanates from a surface (soil, rock, building materials, walls) and accumulates in a container of known volume over a known short duration (typically a few hours). From the accumulated radon concentration the standard describes how to estimate the surface exhalation rate. The method is explicitly estimative and intended for investigations, source searches and comparative studies rather than absolute flux certification.
Key topics and technical requirements
- Measurement principle: enclose a defined surface area with an accumulation container (one open face in contact with the surface), let radon build up for a prescribed accumulation duration, then measure radon activity concentration to derive exhalation rate.
- Applicability: intended for short-term measurements (a few hours) and for exhalation rates greater than about 5 mBq·m‑2·s‑1.
- Equipment and sampling: requirements for accumulation containers, sampling objectives, sampling duration and sampled air volume are described to ensure consistent estimates.
- Detection and measurement: outlines detection method options, measurement procedures and consideration of influence quantities (environmental factors).
- Uncertainty and limits: guidance on expressing results, calculating standard uncertainty, decision thresholds and detection limits; notes that uncertainties may not guarantee inclusion of the true flux value.
- Reporting: specifies information to include in the test report and provides informative annexes with example result sheets and alternative continuous/spot measurement approaches.
- Limitations: does not cover calibration conditions for rate-estimation devices and acknowledges difficulty in quantifying many environmental influences.
Practical applications
- Site investigations to locate or compare radon sources (soil, rock or building materials)
- Short-term field surveys and screening campaigns for radon exhalation hotspots
- Comparative studies of surface exhalation at the same site under different conditions
- Supporting building remediation planning or environmental assessments where surface flux estimates are required
Who uses this standard
- Environmental and radiological protection professionals
- Health physics and radiation measurement laboratories
- Geological and geotechnical survey teams
- Building surveyors assessing radon ingress risks
- Regulators and consultants performing site investigations
Related standards
Keywords: radon-222, surface exhalation rate, accumulation method, EN ISO 11665-7:2015, radon measurement, environmental radioactivity, CEN.