A Field Measurement Device for the Aerosols Used in Mosquito Control

Field droplet sizing is particularly difficult in mosquito control. The droplets produced have a low collection efficiency often leading to inaccurate measurements of the droplet size spectra. An attempt has been made here to find a simple field method that will return a reliable droplet size spectrum for machine calibration and adjustment. Comparisons were made between laser diffraction particle sizers in the laboratory and rotary impingers in the field. This field method is also to be used on an experimental basis to characterize aerosol movement and fate. Miscalculations of droplet spectrum statistics (Dv0.1, Dv0.5, and Dv0.9) occur in the field because the whole droplet size spectrum is rarely sampled due to collection inefficiencies with most samplers. In an attempt to sample a more representative fraction of the spectrum, a rotating impinger has been developed. The sampler has a different size and velocity of collection surface which provides a significant improvement to conventional equipment. Results showed that there was still an underestimation of the smaller droplets due to their low collection efficiency, so a correction factor is still required. This new sampler which operates at 5.6 m/s with a width of 3 mm consistently measured spectra comparable to the laser systems if the Yeomans correction is applied. This sampler could become very useful for measurement of the poly-disperse aerosol used in mosquito control.