Comparison of Particle Count (#cm3 or #ft3) to Mass Weight per Volume (µg-liter)

Frequently, particle counter response levels are compared to light scattering photometer response. Because of the differences in the technologies used this sometimes causes confusion. Particle counters are designed to operate at particulate levels that are significantly lower than those used by photometers. The table below contains data taken from a Condensation Nucleus Counter. This shows the total number of particles (cumulative for ALL particles between approximately 0.1 and 1.0 um) and the corresponding particulate mass weight per unit volume. Please keep in mind that the relationship between particle size and mass is a cube function of the particle diameter.

Increasing or decreasing the diameters or the standard deviation of the particle distribution used for analysis greatly affects the relative mass.

µg/l Total particles per cm3 Total particles per ft3
0.0001 5.56E+00 157,442
0.001 5.56E+01 1,574,417
0.01 5.56E+02 15,744,169
0.1 5.56E+03 157,441,686
1 5.56E+04 1,574,416,860
25 1.39E+06 39,360,421,500
100 5.56E+06 1.57442E+11

The table example data was obtained using an aerosol reagent with a density of 0.819 g/ml, count median diameter of 0.229 µm, mass median diameter of 0.528 um and a count geometric standard deviation of < 1.7. The 25 µg/l data point (in BOLD) was used to extrapolate all other data points referenced within the table.