🌿 Dinitrogen monoxide (N2O) in flue gas from ducts and stacks — sampling, sample conditioning and NDIR analyser, reference method for periodic measurements and AMS calibration, PN-EN ISO 21258

Environment PN-EN ISO 21258

Overview

WHAT THE STANDARD COVERS. We have a preview of ISO 21258:2010 (first edition) — from the table of contents to 6.2.8 (page 7 of 32); PN-EN ISO 21258:2010 introduces the text unchanged (IDT). Scope (Clause 1): a method for sampling, sample conditioning and determination of dinitrogen monoxide (N2O) in flue gas emitted to the atmosphere from ducts and stacks, by the non-dispersive infrared (NDIR) technique, including the sampling and conditioning system. It is a reference method for periodic monitoring and for calibration, adjustment or control of automatic measuring systems permanently installed on a stack; it was tested at a sewage sludge incinerator where the N2O concentration reached about 200 mg/m³. Introduction of the standard: N2O is a greenhouse gas with a global warming potential 310 times that of CO2; increased emissions occur when nitrogenous fuels are burnt below 900 °C and in NOx reduction by SNCR, especially with urea; emissions from stationary sources used to be overestimated because of an artefact of the grab-sampling method; N2O is covered by the EU emission trading scheme, alongside CO2 and methane.

MEASURING SYSTEM (Clauses 5–6 of the preview). A representative volume of flue gas is extracted for a fixed period at a controlled flow rate, dust is removed by filtration before conditioning, and the sample goes to a continuous NDIR analyser; the standard gives performance characteristics of the analyser with minimum criteria, the uncertainty of the method and quality assurance requirements. Probe — corrosion-resistant material (e.g. stainless steel), heated, cooled by an air or water jacket for very hot gases, but not below the acid dew point. Primary filter — ceramic or sintered metal with 10 µm pores, heated above the water or acid dew point. Sample line — PTFE, PFA or stainless steel, kept 15 °C above the dew point of condensable substances. A cooler or permeation drier separates water vapour; a cooling temperature of 2–5 °C is suggested; the cooler and the sample treatment are to prevent N2O forming from NO2 and SO2 dissolved in the condensate. Gas-tight pump (diaphragm, bellows, ejector), secondary filter retaining particles larger than 1 µm (PTFE or borosilicate glass), flow controller and flow meter and — if needed — a converter: a tube with an oxidation catalyst converting CO to CO2 to reduce the influence of this interferent. The span gas for checking a point on the range is usually chosen at about 80 % of full scale; the expanded uncertainty is calculated with a coverage factor k = 2 (95 %).

STATUS (state of the card on 29 September 2026). The card of PN-EN ISO 21258:2010 (English version) has no "Withdrawn" header — the standard is CURRENT: published 09-11-2010, 35 pages, price group Q, Health, Environment and Medicine Sector, KT 280 for Air Quality, ICS 13.040.40, "Introduces: EN ISO 21258:2010 [IDT], ISO 21258:2010 [IDT]"; the PKN search shows no Polish version. ISO 21258:2010 was reviewed and confirmed in 2022 (ISO page of the standard, read on 29 September 2026). The "Scope" field of the card says that the method is "validated for N2O concentrations from 0 mg/m3 to 400 mg/m3" — this sentence is not in Clause 1 of the text, which speaks of a test up to about 200 mg/m³; the preview does not show where the card takes 400 mg/m³ from.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation-scope database, data loaded up to 17 September 2026, read on 29 September 2026). All notations of the number 21258: 33 entries at 11 laboratories. "PN-EN ISO 21258:2010" — AB 409, AB 746, AB 753, AB 782, AB 872, AB 974, AB 994, AB 1066, AB 1624; "PN-EN 21258:2010" (without the ISO element) — AB 550 and AB 833 in all their entries and AB 782 in the AMS entry. The "Laboratories" tab searches for notations BEGINNING WITH "PN-EN ISO 21258" and shows 9 laboratories — checked with the tab query on the labcoda.pl production server on 29 September 2026: 9; AB 550 and AB 833 are only found under "PN-EN 21258" (3, with AB 782). Current scopes on the PCA website (read on 29 September 2026, issues from 07.07.2025 to 22.09.2026): all entries stand in the valid issues, every pair of range limits from the copy appears in the current document and no entry is suspended (suspension footnotes in the scopes of AB 746 and AB 950 concern other entries).

SUBJECT AND RANGES. Flue gas — all 11 laboratories (N2O concentration and usually emission "from calculation"); automated measuring systems (AMS) — 10 laboratories, all except AB 833. The technique is NDIR everywhere. Concentration ranges: lower limits from 0.4 mg/m³ (AB 550) and 0.8 mg/m³ (AB 782) via 1 mg/m³ (AB 833, AB 974, AB 1066), 1.4 (AB 872, AB 1624), 1.6 (AB 409) and 2.0 mg/m³ (AB 753, AB 994) to 4 mg/m³ (AB 746); upper limits from 130 mg/m³ (AB 974) and 150 mg/m³ (AB 409) via 200 (AB 833, AB 1066), 285.0 (AB 1624) and 400 mg/m³ (AB 753, AB 872, AB 994) to 700 mg/m³ (AB 746), 980 mg/m³ (AB 782) and 3900 mg/m³ (AB 550).

ALONGSIDE THIS STANDARD. In the same entry: PN-ISO 10396:2001 — AB 550. Calibration (QAL2) and the annual surveillance test (AST) of automated measuring systems according to PN-EN 14181 with N2O among the components are held by 10 of the 11 laboratories (all except AB 833) — in this role the standard is the reference method, as its scope announces. N2O in flue gas without this standard — Fourier-transform infrared spectroscopy (FTIR): AB 550 (IB_SP_05_10 of 24.06.2024, (0.4 – 400) mg/m³, together with SO2, NO, NO2, NH3, CO, CO2 and CH4), AB 782 (LBŚ-PB-23 issue 4 of 13.07.2020, AMS, (1.97 – 3900) mg/m³), AB 950 (procedure PB20 issue 6 of 13.08.2019, (19.6 – 235) mg/m³) and AB 1207 (NIOSH 3800:2016 with procedure PB-05 issue 2 of 20.01.2025, samples of flue gas and biogas); AB 746 samples N2O into a Tedlar bag according to PB-109/W4 of 01.06.2026 and calculates the emission. All these rows stand in the current PCA scopes without suspension (read on 29 September 2026).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Three places from the standard itself: condensate — N2O can form from NO2 and SO2 dissolved in the condensate, which is why the standard stresses the cooler and the sample treatment (6.2.4); carbon monoxide — the standard treats CO as an interferent and provides a converter oxidizing it to CO2 (6.2.8); temperatures — the probe is heated to avoid condensation inside it, the primary filter is to be above the water or acid dew point, and the line 15 °C above the dew point of condensable substances (6.2.1–6.2.3). The fourth place is the range: the standard describes a test up to about 200 mg/m³, the PKN card speaks of validation up to 400 mg/m³, and the ranges of three laboratories reach 700, 980 and 3900 mg/m³.

WHAT WE DO NOT GIVE. The preview ends at 6.2.8, so we do not give the requirements for the analyser (6.3), responsibilities (6.4), performance criteria and their determination (Clause 7), the uncertainty budget, the measurement procedure with the choice of site and points (Clause 8), quality control (Clause 9), the evaluation in the field, expression of results and report (Clauses 10–12) or the annexes — including the normative Annex B (procedures for determining performance characteristics in the general performance test).

Method principle

A representative gas sample is extracted continuously from the duct or stack at a controlled flow rate. Dust is retained by a heated primary filter (10 µm), the gas flows through a heated line (15 °C above the dew point) to a cooler or permeation drier (2–5 °C suggested) that removes water vapour, then through a secondary filter (> 1 µm) and a flow controller to the NDIR analyser. The analyser measures the absorption of infrared radiation by N2O; where necessary, a catalytic converter oxidizes CO to CO2 to reduce interference. The analyser is checked with zero gas and span gas (usually about 80 % of scale), and the result is given with an expanded uncertainty (k = 2). Criteria for the performance characteristics and the calculation are in Clauses 7–11, beyond our preview.

Applications

• Periodic measurements of N2O emissions from combustion plants (nitrogenous fuels, temperatures below 900 °C, SNCR with urea) and incinerators — 11 laboratories
• Reference method for calibration (QAL2) and annual surveillance tests (AST) of automated measuring systems according to PN-EN 14181 — 10 laboratories
• Greenhouse gas emissions covered by the EU emission trading scheme (N2O alongside CO2 and CH4 — according to the introduction of the 2010 standard)

Key parameters

Standard

Standard number

PN-EN ISO 21258:2010 (wersja angielska; EN ISO 21258:2010, ISO 21258:2010 IDT)

Title (PL)

Emisja ze źródeł stacjonarnych — Oznaczanie stężenia masowego podtlenku azotu (N2O) — Metoda referencyjna: Niedyspersyjna metoda w podczerwieni

Title (EN)

Stationary source emissions — Determination of the mass concentration of dinitrogen monoxide (N2O) — Reference method: Non-dispersive infrared method

Step-by-step procedure

1. Assembling the sample line

   Probe, heated primary filter and line, cooler or drier, pump, secondary filter, flow controller, analyser; inlets for zero and span gas in front of the probe nozzle and upstream of the analyser (Figure 1).

2. Temperatures

   Probe and filter above the (acid) dew point, line 15 °C above the dew point of condensable substances, cooling 2–5 °C.

3. Checking the analyser

   With zero gas and span gas through the whole system; procedures and criteria (Clauses 7–9) beyond the preview — we DO NOT GIVE them.

4. Measurement

   Continuous sampling for a fixed period at a controlled flow rate; measurement site and points (Clause 8) — we DO NOT GIVE them.

5. Result

   Mass concentration of N2O with expanded uncertainty (k = 2); conversion to dry gas and reference oxygen (symbols in Clause 4) and report — Clauses 11–12, beyond the preview.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Work on stacks and flue-gas ducts — hot probes, measurement platforms, toxic gases in the sample; pressurized reference gas cylinders
• SUBSTANTIVE NOTE: the result depends on the sample treatment — N2O can form in the condensate from NO2 and SO2; a converter is needed at high CO

Frequently asked questions