🌿 Potassium hydroxide in workplace air — FAAS, PN-Z-04436

Environment PN-Z-04436

Overview

WHAT THIS STANDARD DESCRIBES. The scope from the PKN catalogue card: "Metoda polega na zatrzymaniu wodorotlenku potasu na filtrze membranowym, mineralizacji próbki w stężonym kwasie azotowym(V), sporządzeniu roztworu do analizy w wodzie. Wodorotlenek sodu w roztworze oznacza się metodą płomieniowej absorpcyjnej spektrometrii atomowej. Najmniejsze stężenie wodorotlenku potasu, jakie można oznaczyć tą metodą, wynosi 0,04 mg/m3" [The method consists in retaining potassium hydroxide on a membrane filter, digesting the sample in concentrated nitric(V) acid and preparing the test solution in water. Sodium hydroxide in the solution is determined by flame atomic absorption spectrometry. The lowest concentration of potassium hydroxide that can be determined by this method is 0.04 mg/m3]. The standard was published on 12 September 2011 in a Polish-language version, has seven pages, is maintained by KT 159 and replaced PN-Z-04005-05:1987. The card has neither a "Withdrawn" header nor a "Withdrawal date" row (checked on 23.09.2026).

AN ERROR ON THE CATALOGUE CARD — AND WHY WE QUOTE IT INSTEAD OF QUIETLY CORRECTING IT. In the scope quoted above, the middle sentence says "**Wodorotlenek sodu** w roztworze oznacza się metodą płomieniowej absorpcyjnej spektrometrii atomowej" [**Sodium hydroxide** in the solution is determined by flame atomic absorption spectrometry] — in a standard whose title, first sentence and last sentence speak of POTASSIUM hydroxide. This is an obvious editorial slip: the card of the standard on potassium carries a sentence copied from the card of the sister standard, PN-Z-04435 on sodium hydroxide, published on the same day by the same committee. We quote it literally for two reasons. First, a reader who consults the card will see the same thing there and must know that this is neither a different method nor a different analyte. Second — and more importantly — **this is a warning about the source**: the catalogue card is a document secondary to the standard, written by the publisher, and it sometimes contains things that are not in the standard. A sentence about the analyte taken from the card instead of from the standard can mislead even when all the other fields of the card are correct.

TWO SISTER STANDARDS, THE SAME LIMIT VALUE, DIFFERENT LIMITS OF QUANTIFICATION. Potassium hydroxide and sodium hydroxide have IDENTICAL values in the list of maximum admissible concentrations: NDS 0.5 mg/m³ and NDSCh 1 mg/m³ (potassium — item 575, sodium — item 576 of the list in the wording given by the regulation of 26 March 2026, Journal of Laws 2026 item 447). The standards were published on the same day and describe the same technique and the same route of sample preparation. Yet the limits of quantification differ: **0.04 mg/m³ for potassium** and 0.024 mg/m³ for sodium. Against the same limit value this gives one twelfth for potassium and one twentieth for sodium. Both methods meet the requirement of PN-EN 482 that quantification should reach one tenth of the limit value, but the margin above this threshold differs twofold — and it results from the sensitivity of atomic absorption for the two elements, not from the quality of the procedure.

WHAT THIS ENTRY DOES NOT GIVE. We do not have the text of the standard — PKN makes it available for a fee. We therefore do not give the sample volume at which the limit of quantification of 0.04 mg/m³ was established, the measurement wavelength or the precision requirements; the card does not contain them. For the sister standard on sodium hydroxide the volume is known from another source and is 720 l — but **it must not be transferred to this standard without checking**, because that would be guessing a condition on which the limit of quantification depends directly.

SCALE OF CITATIONS (reading of 23.09.2026, copy of the database of accreditation scopes). Matching by the BEGINNING of the notation, i.e. the way the "Laboratories" tab searches: 20 entries at 18 laboratories. Across all forms of the core "04436": 21 at 19 — one laboratory is added with the notation "**P N - Z-04436:2011**", in which the PN element is spaced out and a space with a hyphen stands before the letter element. No prefix will cover this notation, so for this standard this laboratory is invisible to the search engine — it is one of the 194 laboratories that we counted as affected by a distortion of the PN element.

Five forms of notation, the balance of occurrences agrees: "PN-Z-04436:2011" 17 times, "PN-Z-04436" without a date 1, "PN-Z-04436:2011 pkt 6" [pkt = clause] 1, a notation with the number of the laboratory's own instruction "IR-18 wydanie nr 1" [wydanie nr = issue no.] 1 and the spaced-out notation mentioned above 1. The ratio of entries to laboratories is 1.1.

Method principle

The potassium hydroxide aerosol is retained on a membrane filter while a known volume of air is drawn through it. The filter is digested in concentrated nitric(V) acid, and the residue is dissolved in water. The solution is introduced into the flame of an atomic absorption spectrometer and the absorbance is measured at the potassium resonance line; the concentration is read from the calibration curve and converted to potassium hydroxide and to the concentration in air. The method thus measures POTASSIUM as an element, and the result is given as the hydroxide — in the same way as the limit value is expressed.

Applications

• Periodic measurements of occupational exposure required by the regulation of the Minister of Health on tests and measurements of agents harmful to health in the working environment
• Alkaline washing and degreasing workplaces, electroplating shops, production of soaps and detergents
• Checking the effectiveness of local exhaust ventilation above tanks with alkaline solutions
• Personal dosimetry in the worker's breathing zone, with sampling in accordance with PN-Z-04008-7

Key parameters

Standard

Standard number

PN-Z-04436:2011 (wersja polska)

Title (PL)

Ochrona czystości powietrza -- Oznaczanie wodorotlenku potasu na stanowiskach pracy metodą płomieniową absorpcyjnej spektrometrii atomowej

Title (EN)

Air purity protection — Determination of potassium hydroxide at workplaces by flame atomic absorption spectrometry

Step-by-step procedure

1. Sampling

   Draw a known volume of air from the worker's breathing zone through a membrane filter.

2. Digestion

   Digest the filter in concentrated nitric(V) acid.

3. Test solution

   Dissolve the residue IN WATER and make up to a known volume.

4. Measurement

   Measure the absorbance of the solution by FAAS at the potassium resonance line; read the concentration from the calibration curve.

5. Calculation

   Convert the potassium content to potassium hydroxide and calculate the concentration in air from the volume of the solution and the volume of air drawn.

6. Reference to the limit values

   Compare the exposure index for the work shift with the NDS of 0.5 mg/m³, and the results of short-term measurements with the NDSCh of 1 mg/m³. State the volume of air drawn in the report — the actual limit of quantification depends on it, and the standard's card does not set it.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Potassium hydroxide is corrosive — carry out sampling at workplaces with an alkaline aerosol wearing safety goggles and gloves
• Concentrated nitric(V) acid: carry out the digestion in a fume hood, wearing chemically resistant gloves and goggles
• Acetylene–air flame: check the tightness of the gas installation and work in accordance with the spectrometer's instructions

Frequently asked questions