🌫️ Ozone in workplace air according to PN-Z-04007-2 — a standard in force, determination in the presence of nitrogen oxides

Environment PN-Z-04007-2

Overview

STATUS (state of the PKN card on 23.09.2026). PN-Z-04007-2:1994 — Polish version. Publication date 15-12-1994, number of pages 4, technical body KT 159 (Chemical and Dust Hazards in the Working Environment), ICS 13.040.30, "Replaces: PN-Z-04007-01:1982 — Polish version". THE CARD CONTAINS NEITHER A "WITHDRAWAL DATE" FIELD NOR A "REPLACED BY" ROW — the standard is in force. This distinguishes it from the neighbouring standards of the same series and the same technical body: the determination of chlorine (PN-Z-04037-03) was withdrawn in 2010, of formaldehyde (PN-Z-04045-02) in 2011, of zinc oxide (PN-Z-04100-03) in 2014.

THE TITLE CONTAINS A CONDITION THAT IS LOST WHEN CITING. The full title speaks of the determination of ozone IN THE PRESENCE OF NITROGEN OXIDES. This is not an ornament: nitrogen oxides occur in the air where ozone is formed — in arc welding, at ultraviolet lamps, at high-voltage equipment — and they interfere with the determination. The standard was written for this case. No entry in the accreditation scopes repeats this condition in the methodology column; it says "Stężenie ozonu" [concentration of ozone] or "Stężenie/zawartość ozonu" [concentration/content of ozone].

WHAT LABORATORIES CITE (measurement on the database of scopes, reading of 23.09.2026): 21 entries at 18 laboratories across all forms of notation; 20 entries at 17 laboratories when matching by the BEGINNING of the notation — and this is the number the "Laboratories" tab shows. The difference is small here, because the notation is exceptionally uniform: "PN-Z-04007-2:1994" stands in 16 entries, and the old scheme ("PN-94/Z-04007-2") in only one. This is the opposite of chlorine and zinc oxide, where the old scheme predominates.

TWO ENTRIES EXCLUDE CLAUSE 7. The notation reads "PN-Z-04007-2:1994 z wyłączeniem pkt. 7" [excluding clause 7], while the standard has four pages. What clause 7 concerns, WE DO NOT GIVE — we did not have the text of the standard. One of these entries gives the number of the laboratory's own procedure next to it ("EV-IR-53 wydanie 1 z dnia 14.10.2019 r." [procedure number with edition and date]).

THE TECHNIQUE AGREES WITH THE TITLE. Twenty entries declare a spectrophotometric method, and the title of the standard speaks of a spectrophotometric method in visible light. Here, unlike the standards on chlorine and formaldehyde (whose titles speak of colorimetry), the name of the technique in the scopes and in the standard is the same.

MEASURING RANGES. Declared: (0.01 – 0.25) mg/m³, (0.0125 – 0.19) mg/m³, (0.0125 – 0.25) mg/m³, (0.014 – 0.200) mg/m³, (0.0150 – 0.450) mg/m³, (0.025 – 0.25) mg/m³; as mass in the sample (0.001 – 0.01) mg, (0.00100 – 0.0100) mg and (0.0010 – 0.015) mg.

AGAINST WHAT THESE NUMBERS APPLY — AND WHY THIS IS SPECIAL HERE. Ozone has an NDS of 0.15 mg/m³ and HAS NO NDSCh or NDSP value; item 451 of Annex No. 1 in the wording given by the regulation of 26 March 2026 (Journal of Laws 2026 item 447, in force since 2 April 2026). The absence of a short-term value means that the assessment rests solely on the eight-hour time-weighted average concentration. THE UPPER LIMITS OF THE RANGES ARE CLOSE TO THE NDS: 0.19 and 0.200 mg/m³ are only a little above 0.15 mg/m³, and one laboratory gives an upper limit of 0.450 mg/m³. With a result exceeding the upper limit of the range, the reading must not be extrapolated — the sampling time must be shortened or the volume of air reduced. Lower limits from 0.01 mg/m³ make it possible to go down to about one fifteenth of the NDS.

LEGAL BASIS FOR CARRYING OUT THE MEASUREMENT. § 16 of the regulation of the Minister of Health on tests and measurements of agents harmful to health in the working environment (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 (…)" [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 laboratories (…)]. Here a Polish Standard DOES exist — and is in force — so it is the method indicated by the regulation, not a substitute solution.

WHAT WE DO NOT GIVE. We did not have the text of the standard. We DO NOT GIVE the way of sampling, the volume of air, the composition of the absorption solution, the way of eliminating the interfering effect of nitrogen oxides, the measurement wavelength or the calculation of the result. Nor do we give the content of clause 7, which two laboratories exclude.

Method principle

Ozone from the air is retained in an absorption solution, and the resulting colouration is measured spectrophotometrically in visible light. The standard is written for the case in which NITROGEN OXIDES are present in the air — i.e. for workplaces where ozone is formed together with them. The concentration in air is calculated by dividing the mass of ozone in the sample by the volume of air sampled. WE DO NOT DESCRIBE THE WAY OF ELIMINATING THE EFFECT OF NITROGEN OXIDES: we did not have the text of the standard, and this is the core of the method.

Applications

• Measurement of the concentration of ozone in workplace air when nitrogen oxides are present
• Workplaces with arc welding, high-voltage equipment and ultraviolet lamps
• Assessment of occupational exposure against the NDS of 0.15 mg/m³ — in the absence of a short-term value
• Reading an accreditation scope in which a standard from 1994, still in force, stands next to ozone

Key parameters

Standard

Standard number

PN-Z-04007-2:1994 (wersja polska)

Title (PL)

Ochrona czystości powietrza — Badania zawartości ozonu — Oznaczanie ozonu w obecności tlenków azotu na stanowiskach pracy metodą spektrofotometryczną w świetle widzialnym

Step-by-step procedure

1. Checking whether the method suits the workplace

   The standard is written for the determination of ozone IN THE PRESENCE OF NITROGEN OXIDES. Before choosing the method, check whether nitrogen oxides occur at the workplace — in arc welding, at ultraviolet lamps and high-voltage equipment they occur together with ozone.

2. Taking the air sample

   Draw the air through the absorption solution under the conditions established in the standard and record the volume of air. We do not give the conditions of the standard — we did not have its text.

3. Spectrophotometric measurement in visible light

   Measure the colouration of the solution against a calibration curve. This technique is declared by 20 entries in the accreditation scopes and is in line with the title of the standard.

4. Converting to the concentration in air

   Divide the mass of ozone in the sample by the volume of air sampled. The lower limits of the laboratories' ranges start at 0.01 mg/m³, the upper ones reach 0.25–0.45 mg/m³.

5. Relating to the limit value

   Compare with the NDS concentration of 0.15 mg/m³ (item 451 of Annex No. 1, wording of Journal of Laws 2026 item 447). There is no short-term value for ozone in the list — an assessment of a short-term rise in concentration cannot be based on an NDSCh, because no such value has been set.

6. Procedure for a result above the range

   The upper limit of the range is sometimes only slightly higher than the NDS. A result above the range requires repeating the measurement with a shorter sampling time or a smaller volume of air — it must not be read from an extended calibration curve.

7. Recording exclusions, if they are in the scope

   Two entries in the scopes cite the standard with clause 7 excluded — if the scope contains an exclusion, the report is to state it.

Required equipment and apparatus

Health and safety (OHS)

• Ozone is strongly irritating to the respiratory tract, and its NDS of 0.15 mg/m³ is one of the lowest in the list — the measurement is made in air that is itself a hazard
• NO short-term value (NDSCh) has been set for ozone — short-term rises in concentration cannot be assessed by comparison with a short-term value, because there is none
• The title of the standard contains the condition "in the presence of nitrogen oxides"; citing the number alone without this condition does not tell the client for what situation the method was written
• The upper limit of the range is sometimes only a little higher than the NDS — a result above the range read from an extended calibration curve looks correct and is not correct
• Excluding clause 7 from a four-page standard means excluding a substantial part of the document — when reading the scope it is worth checking what it concerns

Frequently asked questions