🏭 Hydrogen fluoride (gaseous fluorides) in waste gases — ISO 15713, with sampling according to CEN/TS 17340

Environment ISO 15713

Overview

WHAT THIS STANDARD IS AND HOW IT IS CITED. ISO 15713:2006 is an INTERNATIONAL standard with no counterpart in the collection of Polish Standards — and this is also how accreditation scopes cite it: directly as "ISO 15713:2006". We checked this by a measurement on the database of scopes (22-09-2026): the form "ISO 15713" appears in 120 entries, while the forms "EN 15713", "PN-EN ISO 15713" and "PN-ISO 15713" — not once. This result is worth noting, because with PN-ISO standards that have a Polish counterpart an EN element that is not in the designation is sometimes added; here the laboratories write the number correctly.

JOINT CITATION WITH CEN/TS 17340 — A DIVISION OF ACTIVITIES, NOT AN ALTERNATIVE. Some laboratories cite two documents at once in their scope: "ISO 15713:2006 CEN/TS 17340:2020-09". The distribution of methodologies in the scopes (own measurement, 24 entries with CEN/TS 17340) shows how these documents divide the work: with the joint citation the methodologies are "Pobieranie próbek do oznaczania fluorowodoru" [sampling for the determination of hydrogen fluoride], "Stężenie fluorowodoru" [concentration of hydrogen fluoride], "Stężenie HF" [concentration of HF] and "Emisja HF (z obliczeń)" [emission of HF (calculated)]; with a citation of CEN/TS 17340 alone there is mainly "Pobieranie próbek do oznaczania stężenia fluorowodoru" [sampling for the determination of the concentration of hydrogen fluoride], and at AB 1624 also "Emisja fluorowodoru (z obliczeń)" [emission of hydrogen fluoride (calculated)]. Laboratories therefore treat the CEN/TS above all as a SAMPLING document, and ISO 15713 as the document of the whole method.

A CEN/TS IS NOT A STANDARD — AND FOR THE READER THIS HAS A CONSEQUENCE. A CEN technical specification (CEN/TS) is a document with a lower degree of consensus than a standard: it is issued when the conditions for adopting a standard do not yet exist, and it has a limited period of validity, after which it either becomes a standard or is withdrawn. A laboratory that has a technical specification in its accreditation scope is therefore in a different situation from one that has a standard — the status of the document is worth checking more often. We have not established the current status of CEN/TS 17340:2020-09 or whether work on converting it into a standard is under way (state as of 22-09-2026).

WHAT THE MEASUREMENT CONSISTS OF. A representative, metered sample of gas is drawn through a HEATED PROBE and a filter. Heating the probe matters for the substance of the measurement, not just technically: droplets that may contain dissolved fluorine compounds evaporate in the probe, so that fluorine from the liquid phase reaches the determination instead of settling on the walls. Filtration at a controlled temperature, in turn, removes fluorides bound to dust — that is, it separates what the standard does NOT measure. Gaseous fluorides, more precisely those water-soluble fluorine compounds that pass through the filter, are absorbed in a series of impingers containing sodium hydroxide solution. The fluoride content of the absorption solution is determined with an ION-SELECTIVE ELECTRODE.

THE SAME TECHNIQUE AS IN THE WITHDRAWN WATER STANDARD PN-78/C-04588/03. The final determination is carried out in the same way as in PN-78/C-04588/03 — potentiometrically, with a fluoride ion-selective electrode (that standard has its own entry in this database). The difference lies in what precedes the measurement: for water, the sample is measured after adding an ionic strength buffer; for emissions — the absorption solution from the impingers. The technique that for water was removed from the reference methodologies in favour of ion chromatography therefore remains valid for emissions. This is a good example of the fact that an "outdated technique" is not a property of the technique, but of its assignment to a matrix and a range.

SCOPE OF APPLICATION AND DETECTION LIMIT. The standard is applied to emission sources with a fluoride concentration below 200 mg/m³. The detection limit of the method is estimated at 0.1 mg/m³ for a sample volume of 0.1 m³ — that is, this number is tied to the sample volume and means nothing without it. The ranges declared by laboratories in their accreditation scopes are (0.02–200) mg/m³.

RESULT EXPRESSED AS HYDROGEN FLUORIDE. The content of gaseous fluorides is reported as the mass of hydrogen fluoride (HF) in the stack gas. This is a reference condition without which the number is incomplete: the same fluorine content expressed as F and as HF gives different numerical values. In the accreditation scopes, next to "Stężenie HF" [concentration of HF], there is separately "Emisja HF (z obliczeń)" [emission of HF (calculated)] — a quantity calculated from the concentration and the gas flow, not measured.

SAMPLING CONDITIONS — FROM THE TEXT OF THE STANDARD, CLAUSES 5–7.3. The absorption solution is NaOH at a concentration of 0.1 mol/l (clause 5.1). The sampling train consists of a SERIES OF FOUR IMPINGERS with a convenient capacity of 125–250 ml, connected with materials resistant to HF (polypropylene, polyethylene, Viton); the first two contain 50–100 ml of NaOH solution each (clause 6.4). A filter placed outside the duct is heated to at least 423 K or to a temperature more than 20 K ± 5 K above the dew point — whichever of these two values is HIGHER applies (clause 6.3). The filter must have a retention efficiency of at least 99.5 % for particles with a diameter of 0.3 µm and withstand a temperature 40 K higher than the set temperature; the filter support MUST NOT be made of sintered glass, because the sinter removes gaseous fluorides, i.e. what is to be measured. If fluorides bound to dust make up less than 10 % of the total, the filter may be omitted. The sampling time is AT LEAST 30 MINUTES, and for a cyclic process it must cover at least one full operating cycle of the installation (clause 7.2).

WHAT WE DO NOT GIVE. We had a sample extract of ISO 15713:2006 covering clauses 1–7.3, i.e. the scope, normative references, principle, reagents, apparatus and sampling. We DID NOT HAVE clauses 8, 9 and 10 — the analytical procedure with the ion-selective electrode, the expression of results and the performance characteristics of the method. Everything this entry says about the final determination itself, about calculating the result and about the detection limit therefore comes from secondary sources: documentation of the standard made available by standardisation bodies and the method implementation document (MID) for the MCERTS scheme. Nor did we have the text of CEN/TS 17340:2020-09 — the document is sold for a fee. We have not established the status of CEN/TS 17340 or whether ISO 15713 has a newer edition in preparation. We also looked for the further clauses in the national edition of another country (SIST ISO 15713:2009, reading of 22.09.2026) — that extract reaches LESS FAR, because it ends at clause 6.3. We report the negative result so that nobody searches a second time by the same route.

Method principle

A metered sample of gas is drawn through a heated probe and a filter kept at a controlled temperature: droplets containing dissolved fluorine compounds evaporate in the probe, and fluorides bound to dust are retained on the filter and do not enter the determination. Water-soluble gaseous fluorides pass through the filter and are absorbed in a series of impingers containing sodium hydroxide solution. The fluoride content of the absorption solution is determined potentiometrically with an ion-selective electrode, and the result is expressed as the mass of hydrogen fluoride in the gas.

Applications

• Measurements of hydrogen fluoride emissions from industrial installations covered by an integrated permit
• Monitoring of emissions from glassworks, brickworks and ceramic installations, where fluorine comes from the raw materials
• Measurements at installations producing phosphate fertilisers and processing aluminium
• Distinguishing gaseous fluorides from fluorides bound to dust — the standard measures only the gaseous fraction
• Reading an accreditation scope in which CEN/TS 17340 is cited next to ISO 15713 for sampling

Key parameters

Standard

Standard number

ISO 15713:2006

Title (PL)

Emisja ze źródeł stacjonarnych — Pobieranie próbek i oznaczanie zawartości fluorków gazowych

Title (EN)

Stationary source emissions — Sampling and determination of gaseous fluoride content

Step-by-step procedure

1. Checking the conditions at the emission source

   Establish whether the fluoride concentration is within the scope of application of the standard (below 200 mg/m³) and whether measurement ports and a platform meeting the sampling requirements are available.

2. Preparing the sampling set

   Assemble the heated probe with filter and the series of impingers containing sodium hydroxide solution. Check the tightness of the system and the proper functioning of the gas volume measurement.

3. Sampling

   Draw a metered sample of gas through the probe and the filter for at least 30 minutes, and for a cyclic process for at least one full operating cycle of the installation. Heating the probe ensures evaporation of droplets containing dissolved fluorine compounds; the filter at a controlled temperature retains fluorides bound to dust, which do not enter the determination.

4. Collecting the absorption solution

   After sampling, collect the contents of the impingers quantitatively, rinse the system and make up to a known volume. Both the volume of the gas sample and the volume of the solution enter the calculation of the result.

5. Determination of fluorides

   Measure the fluoride content of the absorption solution with an ion-selective electrode, after adding the ionic strength buffer to samples and standards in the same way.

6. Calculating and expressing the result

   Convert the fluoride content to the mass of hydrogen fluoride in the gas and relate it to the sample volume. When reporting the result, state that it is expressed as HF — the same fluorine content expressed as F gives a different number.

7. Distinguishing concentration from emission

   If the scope includes "Emisja HF (z obliczeń)" [emission of HF (calculated)], remember that this is a quantity calculated from the concentration and the volume flow of the gas, not a measurement result — and mark it in the report with the annotation "(z obliczeń)" [calculated].

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hydrogen fluoride is highly toxic and corrosive, and its effect on tissues can be delayed — work at the emission source requires respiratory and skin protection and a procedure for dealing with contact
• Sodium hydroxide solution is corrosive — fill and empty the impingers wearing safety goggles and chemically resistant gloves
• Sampling at the emission source takes place at height and with hot gases — the rules for working on the measurement platform and protection against burns from the probe apply
• Always report the result with the information that it is expressed as HF and with the gas reference conditions — a number without these indications is not comparable with limit values

Frequently asked questions