Guideline series VDI 4301 describes measurement methods for various indoor air pollutants. This guideline describes a measurement method for the determination of pyrethroids and piperonyl butoxide (PBO). Pyrethroids are organic compounds, which are synthesised through modification and insertion of various functional groups, based on the structure of pyrethrum, a natural insecticide. Piperonyl butoxide (PBO) is mainly added as a synergist to pest control agents containing pyrethrum or pyrethroids and has itself no insecticide effect. In indoor environments, the stability of this compound is comparable with that of long-term pyrethroids.