The invention encompasses 2-N-methyl-propanamine)-3- thiophene, a duloxetine hydrochloride impurity, as well as its use as a reference marker and reference standard. The invention also provides methods of emanating vapour active pyrethroids and the use of packaging means according to the invention for retaining and emanating vapour active pyrethroids. The data record formed in this way is for its part subjected to a stationary multiple cross correlation with respect to the transverse direction. The methods may further include determining a score based on the behavioral, spatial, and reflectance metrics and rejecting or accepting the one or more images based on the score.