ISO 11929-1-2019 PDF

Full title and description

St ISO 11929-1-2019 — Determination of the characteristic limits (decision threshold, detection limit and limits of the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 1: Elementary applications. This document specifies procedures and formulae used in ionizing‑radiation metrology to calculate the decision threshold, detection limit and coverage‑interval limits for non‑negative measurands derived from counting measurements (gross and background counts) and simple evaluation models.

Abstract

ISO 11929-1:2019 (Part 1 of the ISO 11929 series) gives a consistent statistical framework for the calculation of characteristic limits for counting‑type measurements with preselection of time or counts. It covers elementary applications for which uncertainties can be evaluated following the ISO/IEC Guide 98‑3 (GUM / JCGM 2008) approach. The standard addresses net count rates (gross minus background), net activities after calibration and other measurands derived from counting, including the influence of calibration factors, sample treatment and simple models of evaluation. Annexes treat repeated counting measurements and linear analog ratemeter measurements; implementation tools (for example, UncertRadio) are referenced for practical calculation support.

General information

• Status: Originally published (Edition 2, 2019); subsequently superseded by a later edition (ISO 11929-1:2025).
• Publication date: February 2019 (Edition 2, published 13 February 2019).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.240 — Ionizing radiation.
• Edition / version: 2 (2019).
• Number of pages: 41 pages.

Scope

This part of ISO 11929 covers elementary counting measurement situations commonly encountered in ionizing radiation metrology. It provides procedures to compute the decision threshold (critical level), the detection limit (minimum detectable amount or activity) and the limits of the coverage interval for measurands that are non‑negative and derived from combinations of gross and background counts and other model parameters. The document is restricted to cases where uncertainties can be treated within the GUM (ISO/IEC Guide 98‑3 / JCGM) framework. It does not address advanced unfolding methods or more complex measurement models, which are treated in other parts of the ISO 11929 series.

Key topics and requirements

• Definition and calculation of the decision threshold (critical level) for counting measurements.
• Definition and calculation of the detection limit / minimum detectable activity (MDA) for non‑negative measurands.
• Calculation of the limits of the coverage interval for reported measurand values (confidence intervals around measurements).
• Uncertainty evaluation consistent with ISO/IEC Guide 98‑3 (GUM / JCGM), including propagation through simple measurement models.
• Treatment of gross and background count statistics, net count rate calculations and influence of calibration factors and sample processing.
• Special cases: repeated counting measurements (Annex A) and linear analog ratemeters (Annex B).
• Practical calculation guidance and reference to supporting software tools (e.g., UncertRadio) for implementing the procedures.

Typical use and users

ISO 11929-1:2019 is used by national and industrial calibration and testing laboratories, environmental radioactivity monitoring laboratories, nuclear facilities, instrument manufacturers, regulatory bodies, and research institutions. Typical use cases include establishing detection limits for low‑level radioactivity assays, routine environmental and food monitoring, acceptance testing of detectors, and documentation of decision thresholds required for compliance and reporting.

Related standards

ISO 11929-1 forms Part 1 of the ISO 11929 series. Related and complementary standards include other parts of the series (ISO 11929-2, ISO 11929-3, ISO 11929-4), and practical/sectoral standards such as ISO 18589 (environmental radioactivity measurement), ISO 11665 (radon), ISO 9696 / ISO 9697 / ISO 9698 (sewage / monitoring related methods), ISO 10703, ISO 28218 and ISO 7503, which reference or use similar statistical approaches for detection limits and uncertainty evaluation.

Keywords

detection limit, decision threshold, critical level, coverage interval, measurement uncertainty, counting measurements, net count rate, ionizing radiation, minimum detectable activity (MDA), ISO 11929, metrology

FAQ

Q: What is this standard?

A: ISO 11929-1:2019 is Part 1 of the ISO 11929 series; it defines methods to determine characteristic limits (decision threshold, detection limit and limits of the coverage interval) for elementary counting measurements in ionizing‑radiation metrology.

Q: What does it cover?

A: It covers statistical procedures and formulae for counting measurements with preselected time or counts, including treatment of gross and background counts, propagation of uncertainties under the GUM framework, and special cases (repeated counts and analog ratemeters). It is intended for elementary measurement models where uncertainties can be evaluated by standard GUM methods.

Q: Who typically uses it?

A: Calibration and testing laboratories, environmental radioactivity monitoring organizations, nuclear industry laboratories, instrument manufacturers, regulators and metrology institutes use this standard to set and document detection limits, decision thresholds and confidence intervals for radioactivity measurements.

Q: Is it current or superseded?

A: ISO 11929-1:2019 was published in February 2019 (Edition 2). It has since been superseded by a later edition (ISO 11929-1:2025). Users requiring the most up‑to‑date normative text should consult the current edition (the 2025 revision) for any changes or clarifications introduced after 2019.

Q: Is it part of a series?

A: Yes. ISO 11929 is a multi‑part series: Part 1 covers elementary applications (this document), Part 2 addresses advanced applications and uncertainty evaluation extensions, Part 3 treats unfolding methods and multi‑channel spectrometry, and Part 4 provides guidance and worked examples for applying the series.

Q: What are the key keywords?

A: Detection limit, decision threshold, critical level, minimum detectable activity (MDA), coverage interval, GUM, counting statistics, net count rate, ionizing radiation.