Series (Part 4 of 4): Comparing Particle Loss in Transport Tubing for Instruments with Different Flow Rates

Series (Part 4 of 4): Comparing Particle Loss in Transport Tubing for Instruments with Different Flow Rates

Results of Testing
Table 3 shows the particle counts from each instrument for each of the duplicated test runs. This data is normalized to counts per cubic meter (n/m3). The results presented also show the % losses of each test run for the instruments relative to the reference Lasair III 5100. A summary of average losses is given in Table 4.


From the data, all Lasair III particle counters achieved turbulent flow conditions, as all instruments have a Reynolds number > 4000. Therefore the transportation of particles is maximized. However it is a known function of adding tubing to a particle counter that one will experience losses in tubing. The test data showed that these losses are measurable. The following conclusions can be made:

  • Particle losses increase as particle size increases. Each of the instruments demonstrates lower losses in 2 m of tubing for the smallest particles (0.5 µm) than is apparent for the large particles (5.0 µm).
  • The instruments with the higher Reynolds number transport particles more efficiently. The % loss of 5.0 µm particles for the higher flow rate instrument, the Lasair III 5100, is less than the % loss of particles for the lowest flow rate, Lasair III 310C.
  • Average losses for particles in 2 m of transport tubing for large (5.0 µm) particles are between 17% and 27%. This is reflective of previously published data from Particle Measuring Systems3.

Therefore, when choosing a particle counter for different applications, remember that there is a difference between instrument flow rate and potential data, relative to particle losses of the larger particles. For room classification, to either ISO 14644-1 or EU GMP Annex 1, where a single measurement per year is made and that measurement is both of a large sample volume and a critical measurement, the high flow rate Lasair III 5100 is preferred as it both transports particles more effectively and samples the 1 m3 faster.

Particle Measuring Systems recommends minimizing the amount and length of tubing where possible in order to improve true count accuracy.

Thank you for tuning in to this blog series! To download the full paper, click here.

Explore Other Topics

Search Knowledge Center: