🌿 Inhalable fraction of the aerosol (dust) at workplaces — gravimetric method

Environment PN-Z-04507

Overview

The inhalable fraction is — according to the regulation on the maximum admissible concentrations (NDS) and the maximum admissible intensities (NDN) — the fraction of the aerosol entering through the nose and the mouth which, after deposition in the respiratory tract, creates a hazard to health, defined in accordance with the standard PN-EN 481. The standard EN 481 defines the sampling conventions for the inhalable, the thoracic and the respirable fractions as relationships between the aerodynamic diameter of the particles and the mass fraction which is to be collected; for the inhalable fraction the fraction EI = 50·(1 + exp(−0.06·D)) %, where D — the aerodynamic diameter in µm (for D = 10 µm about 77 %, for 100 µm about 50 %), and the convention is not applied to particles above 100 µm.

The standard PN-Z-04507:2022-05 (with the corrigendum Ap1:2022-08) gives the method of determining the inhalable fraction of the aerosol in the air at workplaces by the gravimetric method; it is applied during the control of the sanitary and hygienic conditions. It replaced the previously applied standard PN-91/Z-04030/05 concerning "total dust". The smallest concentration which can be determined depends on the type of sampler, the time of sampling, the type of filter and the scale interval of the balance. The NDS values for dusts (the inhalable and the respirable fraction) are contained in the annex to the regulation on NDS and NDN; the principles of sampling in the working environment and of the interpretation of the results are laid down by PN-Z-04008-7, and the measurement strategy by PN-EN 689.

Method principle

The gravimetric method consists in determining the mass of the particles of the aerosol contained in a unit volume of air (mg/m³). The air tested is drawn at a known volume flow rate over a specified time through a sampler containing a filtering medium (filter), so as to retain the inhalable fraction of the aerosol. The mass of the aerosol retained is determined as the difference in the mass of the filter weighed after the sampling and before it; if the documentation of the manufacturer of the sampler provides for weighing the filter together with the cassette, the filter is weighed with the cassette. The concentration is calculated as the ratio of the mass of the aerosol retained on the filter to the volume of air drawn through the filter: X = (m2 − m1 − B)/V, where m2, m1 — the mass of the filter (or of the filter with the cassette) after and before the sampling [mg], B — the mean change of mass of the blank samples [mg], V — the volume of the air sampled [dm³].

Applications

• Measurements of the concentrations of dusts at workplaces required by the regulation of the Minister of Health on tests and measurements of harmful agents — comparison of the exposure index with the NDS
• Plants with emissions of dusts: the wood, the food (flour dusts), the mineral, the metallurgical and the chemical industries, agriculture
• Assessment of the exposure to dust agents in personal sampling (the head in the breathing zone) and in stationary measurements
• Basis for the assessment of occupational risk: small risk (W ≤ 0.5 NDS), medium (0.5 NDS < W ≤ NDS), large (W > NDS)
• Sampling for further chemical determinations (e.g. of metals) in the dust of the inhalable fraction

Key parameters

Standard

Standard number

PN-Z-04507:2022-05 + Ap1:2022-08

Title (PL)

Ochrona czystości powietrza — Oznaczanie frakcji wdychalnej aerozolu na stanowiskach pracy metodą grawimetryczną

Title (EN)

Air purity protection — Determination of the inhalable aerosol fraction at workplaces by the gravimetric method

Step-by-step procedure

1. Preparation of the filters

   Condition the filters (or the filters with the cassettes, if the manufacturer of the sampler so provides) in a desiccator and weigh them before the sampling (m1). Prepare blank samples — filters which go through the whole route without sampling of air — for determining the mean change of mass B. Switch on the balance with the lead time recommended by the manufacturer and check it with a mass standard; weigh each filter twice and take the mean.

2. Assembly of the sampler

   Mount the filter in the sampler for the inhalable fraction, connect the pump, set and measure the volume flow rate required for the given sampler. Note the temperature and the pressure.

3. Sampling

   In personal sampling place the head in the breathing zone of the worker; in a stationary measurement — at an established point of the workplace. Sample for the time established by the measurement strategy (PN-Z-04008-7, PN-EN 689), so that the mass of dust on the filter exceeds the limit of determination. After the end measure the volume flow rate again.

4. Transport and storage

   Transport and store the filters in closed cassettes in the manner specified in the standard, protecting them against loss of dust; before weighing condition them again under the same conditions as before the sampling.

5. Weighing and calculation

   Weigh the filter after the sampling (m2), calculate V from the averaged volume flow rate and the time of sampling and X = (m2 − m1 − B)/V in mg/m³.

6. Assessment of the exposure

   Determine the exposure index referred to the working shift and compare it with the NDS from the regulation; the conditions are safe where the index does not exceed the NDS, and harmful — where it is greater. Where it is exceeded the employer is to take corrective measures without delay.

Required equipment and apparatus

Health and safety (OHS)

• The dusts of certain materials (hardwood, crystalline silica) are carcinogenic agents — during the sampling and the handling of the filters use protection of the respiratory tract and avoid raising dust again
• Treat the filters after sampling as samples potentially containing harmful substances; do not open the cassettes outside the laboratory
• Fasten the personal pumps so that they do not restrict the movements of the worker or create a risk of catching on machines

Frequently asked questions