🌿 SO₂ in air (UV fluorescence)

Environmental PN-EN 14212

Overview

STATUS (as of 02.11.2026). PN-EN 14212:2025-05 — English version (Polish title in the PKN catalogue: “Powietrze atmosferyczne — Standardowa metoda pomiaru stężenia ditlenku siarki za pomocą fluorescencji w ultrafiolecie”), published on 29.05.2025, implements EN 14212:2024 [IDT]; it replaced PN-EN 14212:2013-02 together with the corrigendum AC:2014-06, both withdrawn on 29.05.2025. The card has no withdrawal note — the standard is current. The European standard EN 14212:2024 (December 2024, approved by CEN on 11.11.2024) superseded EN 14212:2012 with its corrigendum AC:2014; national implementation was due by June 2025 at the latest. The Regulation of the Minister of Climate and Environment of 11.12.2020 on the assessment of levels of substances in air (consolidated text: Dz.U. 2024 item 870), Annex 7 Table 1 item 4, cites as the reference methodology the dated edition PN-EN 14212:2013-02 “Powietrze atmosferyczne — Standardowa metoda pomiaru stężenia ditlenku siarki za pomocą fluorescencji w nadfiolecie” (Ambient air — Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence), withdrawn from the PKN catalogue on 29.05.2025.

SCOPE (EN 14212:2024, clause 1). A continuous method for measuring the SO₂ concentration in ambient air based on ultraviolet fluorescence; the standard gives the performance characteristics and minimum criteria for selecting an analyser by type testing, the evaluation of the suitability of an analyser at a specific fixed site, and requirements during sampling, calibration and quality assurance. It covers concentrations up to 1 000 µg/m³ — the certification range in type testing (1 000 µg/m³ corresponds to 376 nmol/mol) — in rural, urban-background, traffic-oriented locations and locations influenced by industrial sources; results are expressed in µg/m³ at 20 °C and 101.3 kPa. Analysers type tested according to earlier editions can still be used for regulated monitoring.

MEASURING PRINCIPLE (according to the 2012 edition, 5.2). SO₂ molecules excited by UV radiation return to their ground state emitting fluorescence, whose intensity is proportional to the number of molecules in the detection volume and therefore to the concentration. Before the analyser the air passes through a particle filter and a scrubber removing aromatic hydrocarbons; in the reaction chamber it is irradiated with UV light of 200–220 nm, and the fluorescence in the range 240–420 nm is optically filtered and converted to a signal by a UV detector, e.g. a photomultiplier tube. Temperature and pressure are kept constant or the results are corrected; with a volume/volume calibration standard the result is converted to µg/m³.

SAMPLING (according to the 2012 edition, 6.3). A sampling inlet protected against rain, a line as short as practical or a manifold with an additional pump, and a particle filter between the line and the analyser inlet; materials of the inlet and line — PTFE, FEP, borosilicate glass or stainless steel, with SO₂ losses below 2.0 %; the line may be moderately heated to avoid condensation.

TYPE TESTING AND UNCERTAINTY (according to the 2012 edition, clause 5). The analyser characteristics are determined in type testing — laboratory and field tests on at least two analysers by a designated body. Before installation at a site, the expanded uncertainty is calculated with the type-testing results and the conditions of that site; the expanded uncertainty of the method shall not exceed 15 % for fixed measurements and 25 % for indicative measurements (Annex I of Directive 2008/50/EC).

SO₂ LEVELS. Regulation of the Minister of the Environment of 24.08.2012 on the levels of certain substances in air (consolidated text: Dz.U. 2021 item 845): limit values for the protection of human health — 350 µg/m³ for 1 h (permitted exceedance 24 times a calendar year) and 125 µg/m³ for 24 h (3 times); for the protection of vegetation — 20 µg/m³ for the calendar year and the winter season (1.10–31.03); alert threshold — 500 µg/m³ for 1 h, when it persists for three consecutive hours (Annexes 1 and 4). The title of the standard in the assessment regulation uses the systematic name “ditlenek siarki”, while the tables of levels use the name “dwutlenek siarki” — both mean sulfur dioxide.

WHAT WE DO NOT GIVE HERE. Of EN 14212:2024 the foreword, scope, normative references and definitions are available; the measuring principle, sampling, type testing with its criteria (Annex E), installation, field quality control (clauses 9–11) and the list of changes from the 2012 edition (Annex J) are outside it — we give no response time, detection limit, drift, calibration frequency or calibration gas concentrations. The principle and sampling are described according to the 2012 edition.

Method principle

After passing a particle filter and the removal of aromatic hydrocarbons, the air enters the reaction chamber, where UV radiation of 200–220 nm excites the SO₂ molecules; returning to the ground state, they emit fluorescence in the range 240–420 nm, which is optically filtered and measured by a UV detector, e.g. a photomultiplier tube.

The fluorescence intensity is proportional to the SO₂ concentration, so the temperature and pressure in the chamber are kept constant or the results are corrected (according to the 2012 edition, 5.2).

Applications

• Air quality assessment — reference methodology for measuring sulfur dioxide concentrations (Regulation of the Minister of Climate and Environment of 11.12.2020, consolidated text Dz.U. 2024 item 870, Annex 7 Table 1 item 4)
• Sites in rural and urban-background areas, traffic-oriented locations and locations influenced by industrial sources (EN 14212:2024, clause 1)
• Comparison with the limit values and alert threshold for SO₂ (Regulation of the Minister of the Environment of 24.08.2012, consolidated text Dz.U. 2021 item 845)
• Type testing of UV fluorescence analysers and evaluation of their suitability at a site (clause 1)

Key parameters

Standard

Standard number

PN-EN 14212:2025-05

Title (PL)

Powietrze atmosferyczne — Standardowa metoda pomiaru stężenia ditlenku siarki za pomocą fluorescencji w ultrafiolecie

Title (EN)

Ambient air — Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence

Step-by-step procedure

1. Analyser

   An analyser of a type tested according to the standard (laboratory and field tests by a designated body); before installation, calculation of the expanded uncertainty with the type-testing results and the site conditions (2012 edition, 5.3–5.4).

2. Sampling system

   Inlet protected against rain, a line as short as practical of PTFE, FEP, borosilicate glass or stainless steel, a particle filter before the analyser; if necessary moderate heating against condensation (2012 edition, 6.3).

3. Commissioning

   After installation, a test of the correct functioning of the analyser (2012 edition, 5.4).

4. Continuous measurement

   Ultraviolet fluorescence; result in µg/m³ at 20 °C and 101.3 kPa (EN 14212:2024, clause 1).

5. Quality assurance

   Checks and maintenance of the analyser and the sampling system according to clause 9 of the standard, so that the uncertainty of field results does not exceed the requirements (2012 edition, 5.4); the check frequencies are outside the available text.

6. Evaluation of results

   Comparison of 1-hour and 24-hour concentrations with the limit values and the alert threshold (Dz.U. 2021 item 845, Annexes 1 and 4).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• In the available text the standard gives no safety warnings

Frequently asked questions