Abstract
Methomyl concentration levels were monitored before, during and for 24 hours after the spraying of aqueous solutions of the insecticide in a commercial greenhouse containing roses. All measurements were made in real-time using a mobile Atmospheric Pressure Chemical Ionization Mass Spectrometer System. Concentrations detected in the gas phase ranged from less than 1 to a maximum of 7 ppb. After spraying, the methomyl concentrations correlated directly with temperature, degree of air circulation and worker activity within the greenhouse. Methomyl was also present in the aerosol phase in the greenhouse air for at least 24 hours after spraying.