AbstractThe losses of natural pyrethrins, bioallethrin, bioresmethrin and tetramethrin have been measured during thermal fogging using the Swingfog Model SN6 and the Lightweight TIFA. Fogs produced from kerosene solutions of the insecticides containing an internal standard were analysed by gas chromatography. Losses of natural pyrethrins, bioresmethrin and tetramethrin were less than the experimental error showing that these compounds did not degrade in either machine. Losses of bioallethrin were 3.1 and 5.5% in the Swingfog and TIFA respectively but these figures were possibly exaggerated slightly by inefficiencies in the fog sampling technique and it is doubtful if losses of this magnitude would be detected under field conditions.Whilst operating with odourless kerosene, the maximum temperatures recorded within the fogging heads were 120°C in the Swingfog with a flow rate of 351/h and 265°C in the TIFA with a flow rate of 951/
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