Abstract: In a method for the continuous surveillance of the poison content of exhaust gases containing particulate material such as exhaust gases of large furnaces or waste incinerators, a sampling stream is continuously drawn from the exhaust gas stream through a suction line at a rate which corresponds to the exhaust gas stream flow rate, the sampling gas stream is passed through a cyclone in which any coarse particulate material is removed from and collected in a storage container, whereupon the sampling gas stream is passed through fine filter units in which fine particles are removed, a partial gas stream drawn from the particle free sample gas is passed through washing columns in which poisonous gases are washed out of the gas and dissolved in the washing liquid and from an analysis of the coarse and fine particulate material and the washing liquid, a poison distribution standard is determined whereupon for a period of time only coarse particulate material is collected and the poison content of the exhaust gas i