A new method for the determination of the global equivalence ratio (GER) in a microcombustion apparatus as a suitable parameter is introduced in this paper. For this, the burning rate must be determined by continious measurement of the CO2 concentration in the combustion gases. By this, the GER can be calculated, using substance specific data. Investigations with Pyramin DF (herbicide BASF-AG) have shown that the characteristics of the combustion products depend on the condition whether the combustion load ignites or not. In case of ignition the profile of harmful agents can be correlated with the GER. (C) 1999 Elsevier Science Ltd. All rights reserved.