Gravimetric determination of the alveolar
dust fraction (A-dust) according to IFA 6068

Sampling

The following sampling systems are available at the GSA for the sampling of A-dust:

• SG10-2 with FSP-10 (personal sampling)   
• PM4-2 with fine dust head (stationary sampling)
• VC25-2 with fine dust head (stationary sampling) 

Personal sampling is usually performed with the GSA measuring devices SG10-2 and FSP10.

The air loaded with dust is sucked in with a battery-operated pump (SG-10-2) with a volume flow of 10 l/min (600 l/h). We recommend a measurement duration of 4h to reach a volume of 2.4 m³ to be able to detect 1/10 of the limit value (1.25 mg/m³). In a cyclone (FSP-10) the coarse dust is separated in a collecting cup and the air still loaded with A-dust flows through a membrane filter (cellulose nitrate filter with
8 µm pore size and 37 mm diameter) on which the dust is separated.

Site-specific sampling is carried out by means of a volume flow-controlled sampling device with IFA A-dust sampling system (PM4-2A) with a volume flow of 4 m³/h or with IFA A-dust sampling system (VC25-2) with a volume flow of 22.5 m³/h. We recommend a measurement period of 2h. A cellulose nitrate filter of 8 µm pore size and diameter of 70 mm or cellulose nitrate filter of 8
µm pore size and with a diameter of 150 mm, weighed under defined conditions (temperature and humidity), is used as the filter medium.

Analysis

• Electronic analytical balance Mettler Toledo XPR 105 with ionisation module 
• Hydrothermograph (Testo/ testo Saveris 2)

Preparation of the filters

The empty weight of the filters must be determined before sampling.

The filters are laid out for 48 hours in the weighing area at a relative humidity of 40 % – 55 % and a temperature of 22 °C – 28 °C. This storage is called conditioning. After conditioning, the filters are weighed and the results are recorded.

Analytical determination

The loaded filters are laid out for 48 hours in the weighing area, at a relative humidity of 40 % to 55 % and a temperature of 22 °C – 28 °C. After conditioning, the filters are weighed. The blind filters are to be treated in the same manner.

The mass of the A-dust is determined by differential weighing (weighing of the conditioned filters before and after sampling).

The determination limit for the cellulose nitrate filter 37 mm diameter is 0.3 mg, for the cellulose nitrate filter 70 mm diameter 0.6 mg and for the cellulose nitrate filter 150 mm diameter 1.2 mg absolute.

Limit value

The workplace limit value according to TRGS 900 for the respirable fraction (A-dust) is
1.25 mg/m³.