🌿 Determination of the mass concentration of ammonia (NH3) in flue gas from stationary sources (e.g. plants with SCR and SNCR deNOx) by automated measuring systems — extractive (direct or indirect measurement) and in situ — with analysers: differential NOx measurement after conversion of NH3 to NO by chemiluminescence or NDUV, FTIR, NDIR with gas filter correlation (GFC), tuneable laser spectroscopy (TLS); performance criteria: response time ≤ 400 s or ≤ 900 s, repeatability standard deviation, lack-of-fit and 24 h drift ≤ 2 % of the upper limit of the range, cross-sensitivity ≤ 4 %, converter efficiencies, losses and leakage ≤ 2 % of the value; ISO 17179:2016

Environment ISO 17179

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of ISO 17179:2016 (English text; the sample bears the mark of the Slovenian adoption SIST ISO 17179:2019): contents, foreword, introduction, Clauses 1–6 and Clause 7 up to 7.2.1 — the sample ends on page 7. We do not read ongoing quality control (7.2.2), the measurement procedure (8: choice of system, sampling location and points, data collection, calculation), quality assurance (9), test report (10) or Annexes A (differential NOx technique), B (extractive direct NH3 measurement), C (in situ TLS measurement), D (operational gases), E (procedures for determining performance characteristics in the general test), F (examples of results) and G (uncertainty); we know the titles from the contents.

ACCORDING TO THE TEXT OF ISO 17179:2016. The standard was prepared by ISO/TC 146 “Air quality”, Subcommittee SC 1 “Stationary source emissions”. Introduction: SCR and SNCR systems control NOx in flue gas from power plants, waste incinerators and other plants by injecting ammonia or urea; SCR is designed for unreacted NH3 as small as possible (typically below 2–4 mg/m³) with more than 90 % NOx reduction. Scope (1): structure and the most important performance characteristics of AMS for NH3 on stationary sources and the procedures to determine them; methods and equipment, including the sampling and sample gas conditioning system; extractive (direct and indirect) and in situ (direct) systems with analysers: conversion of NH3 to NO or reaction with NO and differential NOx measurement by chemiluminescence (CL) or NDUV, FTIR, NDIR with GFC, TLS; continuous monitoring with permanently installed systems in dry or wet flue gases — for process monitoring, long-term assessment of deNOx performance or emission monitoring; other equivalent methods — if they meet the minimum requirements; calibration with certified gases or comparable methods; the differential CL technique was tested at power plants with NOx up to 50 mg (NO)/m³ and NH3 up to 10 mg/m³ after deNOx, and AMS based on FTIR, NDIR with GFC and TLS have been used for measuring ranges as low as 10 mg (NH3)/m³. References (2): ISO 9169, ISO 14956, ISO 20988. Definitions (3): among others AMS (a system returning in unattended operation a signal proportional to the measurand), in situ AMS, calibration of AMS and validation of AMS (statistical relationship with an independent method applied simultaneously at the same point), efficiencies of the NH3/NO (oxidizing), NH3/N2 (reducing) and NO2/NO converters, interference, lack-of-fit (systematic deviation of the calibration function from reference material values — in everyday language “linearity”), period of unattended operation, reference gas, span gas (often around 70–80 % of full scale), zero gas, response time (sum of lag time and rise or fall time). Symbols (4): molar mass of NH3 17.031 g/mol, molar volume 22.4 l/mol, standard conditions 273.15 K and 101.325 kPa, reference conditions — additionally corrected for O2 and H2O. Principle (5): extractive systems take a representative sample with a probe and convey it through the sampling line and conditioning system to the analyser; in situ systems require no sample processing, but a representative place in the stack. Systems (6): NH3 is a condensable and highly reactive component — condensation, deposition and loss of ammonium compounds in the line easily compromise sample integrity. Criteria (7.1, Table 1): response time ≤ 400 s (emission monitoring) or ≤ 900 s (long-term changes of deNOx, especially decreasing catalyst activity); repeatability standard deviation in the laboratory at zero and span ≤ 2 % of the upper limit of the lowest measuring range used; lack-of-fit ≤ ±2 %; zero and span drift in 24 h ≤ ±2 %, over the period of unattended operation ≤ ±3 %; sensitivity to pressure (change of 2 kPa) and ambient temperature (change of 10 K) ≤ ±3 %; sensitivity to voltage ≤ ±2 % per 10 V (at 200 V); cross-sensitivity ≤ 4 %; converter efficiency NO2/NO ≥ 95 %, NH3/NO ≥ 90 %, NH3/N2 ≥ 95 %; losses and leakage of the line ≤ 2 % of the measured value; beam excursion of cross-stack in situ AMS ≤ 2 %; the upper limit of the lowest range is chosen so that results lie within 20–80 % of the range. Test (7.2.1): the characteristics are determined in the general performance test according to Annex E, and the ambient conditions are documented.

STATUS (as of 03.10.2026). The PKN search engine (query “17179”, 03.10.2026) shows no introducing standard — laboratories cite the ISO document. We did not read the status of ISO 17179:2016 in the iTeh catalogue: since 03.10.2026 the catalogue pages require a browser with scripts; the sample shows the Slovenian adoption SIST ISO 17179:2019.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 03.10.2026). The number 17179 appears in 8 records at 2 laboratories: AB 550 (5) and AB 782 (3). In the current PCA documents (read 03.10.2026; AB 782 issue no. 24 of 10.10.2025, AB 550 issue no. 33 of 22.09.2026) the number appears at the same 2 laboratories; in every document the number of page markers equals the number of PDF pages, without repetitions; a search of all PCA documents downloaded from BIP on 03.10.2026 found no laboratories outside the database copy. The form “ISO 17179:2016” at both; at AB 782 together with procedure LBŚ-PB-23 issue 4 of 13.07.2020. None of these items is suspended (the word “zawieszonego” in the AB 550 document refers to suspended particulate matter PM10 and PM2.5). The “Laboratories” tab (query “ISO 17179”) shows both laboratories — checked by a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). AB 550: flue gas and automated monitoring systems (AMS) — NH3 concentration by FTIR (0.1–389) mg/m³ and by tuneable laser spectroscopy TLS (0.06–389) mg/m³, NH3 emission by calculation. AB 782: flue gas and AMS — NH3 concentration by FTIR (0.38–38) mg/m³, NH3 emission by calculation.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Sampling line: NH3 condenses and reacts, so losses in the line and conditioning bias the result low without a trace in the reading itself — the criterion for losses and leakage is ≤ 2 % of the value (6.1, Table 1). Differential technique: the NH3 result is the difference of two NOx measurements and depends on the converter efficiencies (NH3/NO ≥ 90 %, NO2/NO ≥ 95 %) — with little NH3 and much NOx the difference is small (Table 1, 1). Range: criteria are expressed relative to the upper limit of the lowest range used, and results should lie within 20–80 % of the range (7.1) — a range of (0.06–389) mg/m³ is a span requiring separate working ranges. Response time: ≤ 400 s applies to emission monitoring, ≤ 900 s only to long-term assessment of deNOx (Table 1). Conditions: concentration at standard conditions and at reference conditions (corrected for O2 and H2O) are different quantities (4). Field of use: AMS based on FTIR, NDIR with GFC and TLS have been used at ranges from 10 mg (NH3)/m³, while typical SCR slip is 2–4 mg/m³ (introduction, 1).

WHAT WE DO NOT GIVE. We do not quote the performance test procedures (Annex E), the description of individual techniques (A–C), operational gases, frequency of checks, calculations or the uncertainty budget — they lie outside the sample. We do not summarize ISO 9169, ISO 14956 or ISO 20988 in this entry. We do not give emission limit values for ammonia.

Method principle

Flue gas is drawn with a probe through a line and conditioning system to the analyser (extractive system) or measured directly in the stack (in situ system). NH3 is determined directly — by infrared absorption (FTIR, NDIR with GFC) or laser spectroscopy (TLS) — or indirectly: after conversion of NH3 to NO as the difference of two NOx measurements by chemiluminescence or NDUV. The system must meet the performance criteria of Table 1, checked in the general performance test and in ongoing quality control.

Applications

• Ammonia slip after SCR and SNCR installations at power plants, waste incinerators and other sources (introduction, 1)
• Process monitoring, long-term assessment of deNOx and emission monitoring (1)
• Performance testing and control of automated NH3 measuring systems (7)
• Flue gas and AMS — 8 accreditation scope records of 2 laboratories in PCA

Key parameters

Standard

Standard number

ISO 17179:2016

Title (PL)

Emisja ze źródeł stacjonarnych — Oznaczanie stężenia masowego amoniaku w gazach odlotowych — Charakterystyki zautomatyzowanych systemów pomiarowych

Title (EN)

Stationary source emissions — Determination of the mass concentration of ammonia in flue gas — Performance characteristics of automated measuring systems

Step-by-step procedure

1. Choice of system and range

   Upper limit of the lowest range so that results lie within 20–80 % (7.1). ISO 17179:2016 — no PN (03.10.2026).

2. General performance test

   Determination of the Table 1 characteristics according to Annex E (7.2.1; annex outside the sample).

3. Installation

   Representative sampling location and points (5; 8.3 outside the sample).

4. Continuous measurement

   Data collection, conversion to standard or reference conditions (4; 8.4–8.5 outside the sample).

5. Quality control

   Ongoing control, calibration, validation and uncertainty (7.2.2, 9 — outside the sample).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Ammonia is a reactive and condensable component — losses and leakage of the sampling line limited to 2 % of the value (6.1, Table 1)

Frequently asked questions