Output Distribution of a Collison Nebulizer

A Note on the Output Distribution of the Collison Nebulizer
Created, October 2006

The particle size output of the Collison nebulizer is expressed as the Mass Median Diameter (the median point of the distribution) and the Geometric Standard Deviation (the width of the distribution. A value of 1 would mean that all the particles are the same diameter).

Common abbreviations are MMD and GSD. The “correct” values for the Collison are dependent upon the liquid and how the distributions are measured. There are over 600 web references to the Collison and a wide range of values are available. Having manufactured the Collison nebulizer for over 30 years we believe that for non volatile liquids the MMD is 2.5μm and the GSD is approximately 1.8
Using these figures it is possible to estimate the range of particles being generated. These numbers are for a normal distribution:

For 1 standard deviation which is 68% of the distribution the diameters will vary from 4.5 μm down to 1.4 μm.

For 2 standard deviations which are 95% of the distribution the diameters will vary from 9.0 μm down to 0.78 μm.

For 3 standard deviations which are 99% of the distribution the diameters will vary from 16.2 μm down to 0.43 μm.

This effectively illustrates that approximate range of suspended particles which can be attempted with the collison.