In-field measures of physical spray concentration do not tend to correlate well with caged insect mortality data. This is partly due to the reduced penetration of the spray into the cage. Spray penetration is hindered by the structure of the cage. Wind tunnel studies were conducted to investigate the accuracy of those calculations developed to correct for filtration levels in caged mosquito bioassays. Zenivex E20 (Etofenprox) was applied at rates ranging from an LD 10 to an LD 90. Three cage types were used, each with different penetration levels. The dose approaching the cage was converted to the dose entering the cage using cage penetration data from previous research. The penetration conversion factor returned a data set that directly correlated dose with mosquito mortality (R 2 = 0.918). The mortality percent was a function of the dose within the cage. The mesh type acted as a regulator. Although the conversion factor was effective, the differences between cages was not always significant due to within-group variation.