Particle Settling Velocities

Particle diameter (µm): Setting Velocity (m/s): Setting Velocity (mm/hr)
0.05 3.85E-07 1.39
0.06 4.75E-07 1.71
0.08 6.69E-07 2.41
0.1 8.82E-07 3.18
0.15 1.50E-06 5.40
0.2 2.26E-06 8.14
Typical Concept particle    
0.3 4.21E-06 15.16
0.4 6.76E-06 24.34
0.5 9.91E-06 35.68
0.6 1.37E-05 49.32
0.8 2.30E-05 82.80
1 3.48E-05 125.28
1.5 7.47E-05 268.92
2 1.30E-04 468.00
3 2.85E-04 1026.00
4 5.00E-04 1800.00
5 7.76E-04 2793.60
Typical competitor particle size    
6 1.11E-03 3996.00
8 1.96E-03 7056.00
10 3.06E-03 11016.00
15 6.84E-03 24624.00
20 1.21E-02 43560.00
30 2.72E-02 97920.00

The terminal settling velocity of an aerosol or "artificial smoke" particle increases rapidly with particle size. The settling velocity is proportional to the square of the particle diameter, although sub micron particles, such as those produced by Concept systems require the use of slip correction factors.

Calculated for standard density spheres at 293 K [20° C] and 101 kPa (1 atm).
"Aerosol Technology", William C. Hinds, Wiley-Interscience, 1999

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Testimonials

Royal Air Force

Following the development by Concept of a sub micron smoke system running off the aircraft power supply, for the purpose of leak testing large volume aircraft.

The resulting report noted:

"With the visual aid of white smoke emitting from leakage areas, this was a quick and easy task to accomplish (< 10 minutes)."

It went onto conclude:

"Use of smoke as a means by which to detect cabin pressurization leaks has been shown to be extremely effective and is unquestionably superior to any alternative detection method used to date."