Testing to Demonstrate Losses in 2-Meter-Long Tubing
Each of the above flow rate instruments was tested against a reference Lasair III 5100 particle counter. This reference unit has the highest volume and flow rate and therefore improves statistical significance due to the number of particles measured in a single sample period. Prior to testing, all Lasair III’s were calibrated in accordance to the ISO 21501-4 standard for the calibration of aerosol particle counters6. This base-lined all particle counters such that no significant instrument-to-instrument error existed.
The reference unit was placed directly beneath the outlet of the HEPA filtered air supply and had no sample tubing attached (Figure 2). Each of the units under test: Lasair III 310C, Lasair III 350L and the Lasair III 5100, had 2 meters (2 m) of tubing attached and the inlet of this tubing was located adjacent to the reference unit input. This minimized any sample errors and ensured that the same number of particles was delivered to each transport mechanism, tubing, or directly to the sample inlet.
To minimize the particle sizing error, only NIST traceable PSL (Polystyrene Latex Spheres) and DRI-CAL particle size standards were used. Three particles were chosen for testing: 0.5 µm and 5.0 µm. The size standard aerosol mist was generated using the PMS PG-100 Particle Generator, which nebulizes and dries the particles prior to delivery into the HEPA filtered air flow and supplies the particles to the test instruments. The larger 5.0 µm DRI-CAL particles were generated using the PMS Large Particle Generator, which uses shear forces to deliver individual particles to the test instruments, also via the HEPA filtered air.
The 2 m sample tubing selected was Excelon Bev-A-Line® XX. Bev-A-Line tubing is preferred as it is semi-rigid tubing, thus minimizing the risk of kinks in the tubing, and the inner surface is lined with a HYTREL® polymer that offers a very low friction surface suitable for the transportation of particles.
The next installment will discuss the results of testing and their conclusions. To download the full paper, click here.
