ISO 11665-3:2020

Overview

ISO 11665-3:2020 - Measurement of radioactivity in the environment - Air: radon-222 - Part 3 defines a spot measurement method for determining the activity concentration of short‑lived radon-222 decay products and for calculating the potential alpha energy concentration (PAEC). The standard provides guidance for short-duration air sampling (sampling at a given place for several minutes), device use conditions, measurement procedures and how to report results for rapid on‑site assessment. It is explicitly intended for spot checks (not for estimating annual exposure) and applies to air samples with PAEC greater than 5 nJ/m3. The document does not cover contributions from radon‑220 decay products.

Key technical topics and requirements

• Measurement principle: Sampling of airborne short‑lived radon decay products followed by alpha detection to calculate PAEC.
• Sampling: Practical recommendations for sampling location, installation of sampling system, sampling duration (short, on the order of minutes) and sampled air volume suitable for spot measurements.
• Detection and counting: Guidance on detection methods (e.g., gross alpha counting) and counting protocols; Annexes include example protocols and the Thomas protocol.
• Calibration and performance: Requirements for instrument calibration, influence quantities, and conditions of use to ensure valid spot measurements.
• Expression of results: How to express PAEC, estimate standard uncertainty, and determine decision thresholds and detection limits for spot measurements.
• Limitations: The standard emphasizes that results are for rapid assessment only and cannot be extrapolated to annual PAEC or used alone to decide mitigation actions for long‑term exposure.

Practical applications and users

Who uses ISO 11665-3:2020:

• Environmental and radiological testing laboratories performing on‑site radon decay product checks.
• Radiation protection professionals conducting rapid indoor air assessments.
• Building inspectors and consultants needing spot measurements for diagnostics or follow‑up checks.
• Instrument manufacturers and calibration laboratories implementing device performance criteria.
• Emergency responders assessing short‑term elevated PAEC conditions.

Typical applications:

• Rapid spot checks of indoor air PAEC where short‑term decisions or diagnostics are needed.
• On‑site surveys in workplaces or public buildings to identify areas with elevated radon decay product concentrations.
• Validation and commissioning of radon decay product monitoring instruments.

Related standards

• ISO 11665-1 (origins and measurement methods overview)
• ISO/IEC 17025 (competence of testing/calibration laboratories)
• IEC 61577 series (requirements for radon and radon decay product measuring instruments)

Keywords: ISO 11665-3:2020, radon-222, potential alpha energy concentration, PAEC, spot measurement, radon decay products, radon monitoring, rapid assessment, detection limit, calibration, decision threshold.