🟡 Chlorine in workplace air according to PN-Z-04037-03 — a two-page standard from 1975, withdrawn in 2010, still in 29 scopes

Environment PN-75/Z-04037

Overview

STATUS (state of the PKN card on 23.09.2026). PN-Z-04037-03:1975 — Polish version — is WITHDRAWN. Publication date 30-07-1975, WITHDRAWAL DATE 30-11-2010, number of pages 2, technical body KT 159 (Chemical and Dust Hazards in the Working Environment), ICS 13.040.30. THE CARD CONTAINS NO "REPLACED BY" ROW — PKN withdrew the standard without indicating a successor. Nor do we indicate a successor: we did not find a document of which it could be said that it replaces it, and we will not guess.

WHAT LABORATORIES CITE (measurement on the database of scopes, reading of 23.09.2026, across all forms of notation): 32 entries at 29 laboratories. When matching by the BEGINNING of the notation in the form of the old scheme ("PN-75/Z-04037") — 24 entries at 22 laboratories, and this is the number the "Laboratories" tab shows for this entry.

THE FORM OF NOTATION IS DECISIVE HERE, NOT DECORATIVE. The same standard has two numbering schemes in the scopes: the old "PN-75/Z-04037/03" (17 entries, plus ".03" — 4 and "-03" — 1) and the new "PN-Z-04037-03:1975" (7 entries). A search by the new scheme finds SEVEN entries out of thirty-two — i.e. less than a quarter. That is why the field by which this entry searches for laboratories has the form of the old scheme.

TWO PAGES OF THE STANDARD, AND ONE LABORATORY EXCLUDES A CLAUSE FROM IT. Among the notations there is "PN-75/Z-04037/03 z wyłączeniem pkt. 5d" [excluding clause 5d]. The standard has two pages — so the exclusion concerns a fragment of a clause in a two-page document. We do not know the content of this clause: we did not have the text of the standard.

THE TITLE SAYS "COLORIMETRIC", THE SCOPES SAY "SPECTROPHOTOMETRIC". The title of the standard from the PKN card reads: "Determination of chlorine at workplaces by the colorimetric method with methyl orange". In the accreditation scopes, the technique "Metoda spektrofotometryczna" [spectrophotometric method] stands next to this standard in 29 entries. We do not settle whether laboratories describe the same activity with a newer word or carry out the measurement differently from how the standard describes it — we did not have the text of the standard. We note the discrepancy in naming because the reader of a report sees in it the "spectrophotometric method" and a citation of a document whose title says something else.

THE MEASURING RANGES DIFFER BETWEEN LABORATORIES MANY TIMES OVER. Declared in the scopes: (0.05 – 1.75) mg/m³, (0.069 – 3.33) mg/m³, (0.07 – 1.4) mg/m³, (0.07 – 5.0) mg/m³, (0.055 – 10) mg/m³, and converted to mass in the sample: (0.0002 – 0.007) mg, (0.0004 – 0.05) mg and (0.25 – 10) µg. The upper limit differs between laboratories almost sevenfold, the lower — more than threefold. THE MEASURED QUANTITY IS THE SAME, but the range results from the volume of air sampled and from the instrument used, not from the standard: the mass in the sample divided by the volume of air gives the concentration, so a laboratory that samples more air goes lower.

AGAINST WHAT THESE NUMBERS APPLY. The maximum admissible concentration of chlorine [7782-50-5] is 0.7 mg/m³ (NDS), and the maximum admissible short-term concentration — 1.5 mg/m³ (NDSCh); item 84 of Annex No. 1 to the regulation on maximum admissible concentrations and intensities, in the wording given by the regulation of 26 March 2026 (Journal of Laws 2026 item 447), which entered into force on 2 April 2026 and replaced THE WHOLE of Annex No. 1. Without stating against which limit value the result is related, the measuring range alone says nothing about the fitness of the method: a laboratory with a lower limit of 0.07 mg/m³ measures one tenth of the NDS, and a laboratory with a lower limit of 0.05 mg/m³ — one fourteenth.

WHY A WITHDRAWN STANDARD STILL STANDS IN THE SCOPES. The regulation of the Minister of Health on tests and measurements of agents harmful to health in the working environment provides in § 16 (consolidated text — Journal of Laws 2025 item 949): "Badania i pomiary wykonuje się zgodnie z metodami określonymi w Polskich Normach, a w przypadku braku takich norm, metodami rekomendowanymi i zwalidowanymi przez laboratoria, o których mowa w § 15 ust. 1 i ust. 2 pkt 1" [Tests and measurements are carried out in accordance with the methods specified in Polish Standards, and in the absence of such standards, with methods recommended and validated by the laboratories referred to in § 15(1) and (2)(1)]. So the regulation does not require the standard to be current — it requires a method from a Polish Standard, and where there is none, a validated method. WHAT WE DO NOT SETTLE: whether the withdrawal of a standard by PKN means "absence of a Polish Standard" within the meaning of this provision. This is a question of the interpretation of the regulation, not of the status of the document, and there is no answer to it here.

WHAT THIS MEANS FOR THE READER OF A REPORT. A citation of "PN-75/Z-04037/03" in a report from 2026 is a citation of a document withdrawn fifteen years ago, issued in 1975 and two pages long. This does not mean that the result is bad — it means that the description of the method the laboratory uses comes largely from outside this document: from its own, validated procedure. In four entries in the scopes, precisely the number of such a procedure stands next to the standard ("PB-12 wydanie 2 z dnia 01.08.2023 r.", "PB-27 wydanie 2 z dnia 07.01.2025 r.", "PB-SP-01 wersja 03 z dnia 03.02.2025 r.", "PA-60 wydanie 1 z dnia 04.11.2024 r." [procedure numbers with edition/version and date]).

WHAT WE DO NOT GIVE. We did not have the text of the standard — neither the 1975 edition nor the description of its clause 5d. We DO NOT GIVE the conditions of sampling the air, the volume of air drawn, the composition of the absorption solution, the measurement wavelength or the way of calculating the result, because we did not see them. What we know about the method comes from the title of the standard (colorimetry with methyl orange) and from the technique column in the accreditation scopes.

Method principle

Chlorine present in the air is retained in an absorption solution, and the resulting colouration is compared with a standard — the standard calls this the colorimetric method with methyl orange. In their scopes, laboratories declare a spectrophotometric measurement. The result is given as the mass of chlorine in the sample, and the concentration in air is obtained by dividing this mass by the volume of air drawn through the absorber — which is why the lower limit of the range depends on the volume sampled, not on the standard itself. WE DO NOT DESCRIBE THE MEASUREMENT PRINCIPLE IN DETAIL: we did not have the text of the standard.

Applications

• Measurement of the concentration of chlorine in workplace air
• Assessment of occupational exposure against the NDS and NDSCh values for chlorine
• Reading an accreditation scope in which a standard withdrawn in 2010 stands next to chlorine
• Checking whether the declared measuring range reaches below one tenth of the limit value

Key parameters

Standard

Standard number

PN-Z-04037-03:1975 (wersja polska)

Title (PL)

Ochrona czystości powietrza — Badania zawartości chloru — Oznaczanie chloru na stanowiskach pracy metodą kolorymetryczną z oranżem metylowym

Step-by-step procedure

1. Checking which document stands in the scope

   Before citing, check whether it is PN-Z-04037-03:1975, most often written in the old scheme PN-75/Z-04037/03. The standard has been withdrawn since 30-11-2010, and its card does not indicate a successor.

2. Establishing the basis for carrying out the measurement

   If the laboratory carries out the measurement according to its own test procedure, its number and edition should stand in the reference documents next to the standard — as four entries in the scopes do. § 16 of the regulation on tests and measurements permits validated methods in the absence of a Polish Standard.

3. Taking the air sample

   Draw the air through the absorption solution under the conditions established in the procedure and RECORD the volume of air — without it the mass of chlorine in the sample cannot be converted into a concentration. We do not give the conditions of the standard, because we did not have its text.

4. Measuring the colouration

   Measure the colouration of the solution after the chlorine has been absorbed. The accreditation scopes declare a spectrophotometric technique; the title of the standard speaks of a colorimetric method with methyl orange.

5. Converting to the concentration in air

   Divide the mass of chlorine in the sample by the volume of air sampled. It is at this stage that the difference in ranges between laboratories arises: with the same determinable mass, a larger volume of air gives a lower concentration limit.

6. Relating to the limit values

   Relate the result to the NDS of 0.7 mg/m³ and the NDSCh of 1.5 mg/m³ for chlorine (item 84 of Annex No. 1, wording of Journal of Laws 2026 item 447). In the report, indicate separately the reference document for the measurement and separately the act from which the limit value was taken.

7. Recording exclusions, if they are in the scope

   One entry in the scopes cites the standard "z wyłączeniem pkt. 5d" [excluding clause 5d] — if the scope contains an exclusion, the report is to state it.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Chlorine is a gas that irritates the respiratory tract — the measurement is carried out where this gas is present, so the respiratory protection measures provided for the workplace apply
• The standard has been withdrawn since 30-11-2010, and its card does not indicate a successor — citing it without indicating the laboratory's own procedure does not tell the reader where today's description of the method comes from
• A measuring range given without the limit value does not indicate the fitness of the method: only relating it to the NDS of 0.7 mg/m³ shows whether the laboratory goes low enough
• A search by the new numbering scheme ("PN-Z-04037-03:1975") misses most of the laboratories that have this method in their scope — when checking who carries it out, one must search by both schemes
• The upper limit of the range is sometimes lower than the NDSCh of 1.5 mg/m³ multiplied by a margin — a result above the range requires dilution or a shorter sampling, not extrapolation of the curve

Frequently asked questions