BS/EN 17199-5-2019 pdf download.Workplace exposure – Measurement of dustiness of bulk materials that contain or release respirable NOAA or other respirable particles Part 5: Vortex shaker method.
6.2.6 Conductive flexible tubing, carbon impregnated.
To minimize particle losses due to electrostatic effect in sampling lines that convey the released aerosol to the nieasuring instruments and sampling devices, carbon impregnated conductive flexible tubing shall be employed.
To minimize particles losses in sampling lines in which the released aerosol is transported to the measuring instruments and sampling devices, tube lengths and bends in the conductive flexible tubing shall be kept to a minimum.
6.2.7 Respirable cyclone, made of stainless steel.
A respirable cyclone is used as a sampler for sampling the respirable aerosol fraction in configuration A (see Figure 5) and which acts as a particle size pre.separator in configuration B (see Figure 6).
The cyclone shall collect the respirable fraction, as defined in EN 481, at 4,2 1/mm with a performance
as stipulated in EN 13205-2.
For configuration A (see Figure 5), the cyclone is equipped with two-piece air sampling cassettes (see
6.2.8). The assembly is then connected to a sampling pump that operates at 4,2 1/mm.
For configuration B (see Figure 6), conductive flexible tubing (see 6.2.6) shall be used to connect all parts of the instrument.
The axis of the cyclone shall be kept vertical.
6.2.8 Air sampling cassette
25 mm- or 37 mm-air sampling cassettes (two-piece open-faced configuration) containing a preweighted [lIter [or gravimetric analysis shall be used to collect particles in the respirable cyclone in configuration A of the dustiness test (see 6.2.4 and Figure 5).
Air sampling cassettes commonly used for collection of airborne particles are prone to bypass leakage if the cassettes are not properly assembled. Leakage around the filter will result in a loss of particles that should have been collected onto the filter, resulting in a measurement that underestimates the mass of released particles. Therefore, assembly of sampling cassettes shall be performed using a press. A leak testing shall be performed in ensure proper cassette assembly.
6.2.10 Time- and size-resolving aerosol instrument
For the measurement of the number-based particle size distribution of the airborne particles, one time- and size-resolving aerosol instrument covering the particle size range from about 10 nm up to about 10 urn shall be preferred over the use of two instruments, except lithe two instruments measured the same equivalent diameter (i.e. aerodynamic diameter).
The measurement of the number-based particle size distribution in aerodynamic equivalent diameter shall be preferred and shall be performed with a time step oil s.
The aerosol flowrate should be 2,5 1/mm.
The dilution tlowrate should be 7,5 1/mm.
NOTE I So far, the only instrument that can respond to these requests is the Electncal Iow Pressure Impactor (ELPI9. This time-resolved low pressure cascade impactor operates at 10 1/mm. To prevent overloading and bounce of sampled particles it is advised to use sintered oiled collection plates with the ELPI*,
NOTE 2 In the ELPl, the number concentration in each channel Is calculated from the measured current by applying the charger efficiency curve which is dependent on mobility-equivalent diameter, itself related to the aerodynamic diameter. Therefore, it is necessary that the density which relates these two equivalent diameters is known to calculate the number concentration in each channel The density mentioned here corresponds to the effective density of airborne particles, which is theoretically dependent on particle diameter (the larger the agglomerates and aggregates, the smaller their effective density; the closer to the primary particle diameter, the closer to the material density of the compound), see 151 and 161. Concerning the ELPI’, the value considered for the density can have a strong impact on the number concentration. Over the particle size range covered by the ELPI and a range of density from 0.1 g/cm3 to 10 g/cm’, the under estimation or overestimation can reach up to a factor of 25. Despite this, the effect on relative particle size distributions is limited and the modal aerodynamic equivalent diameters are therefore less affected.
The measurement of the mass-based particle size distribution using low pressure cascade impactors is not compulsory but can provide complementary information to the number-based particle size distribution. Low pressure cascade impactors with at least five stages below 1 pm and three stages above 1 pm shall be preferred in order to have a good description of the particle size distribution of the released aerosol.
6.2.11 Aerosol sampler for analytical electron microscopy analysis
For the collection of airborne particles for subsequent observations and analysis by analytical electron microscopy, a TEM-grid holder operating at I I/mm can be used (see Annex B). If this collection is not carried out (as it is optional), an air sampling cassette (see 6.2.8), 25 or 37 mm, equipped with a filter shall be used Instead in order to have the same flow rates in the test apparatus. Given the generally short sampling time (about 10 s), the use of a TEM-gnd holder necessarily requires a by-pass system, equipped with an air sampling cassette (6.2.8) in order to keep a constant flow through the respirable selector, as shown in Figure 4.BS/EN 17199-5-2019 pdf download.