The invention relates to a method for supplying an internal combustion engine with conditioned combustion gas, involving the supply of humidity and/or temperature-conditioned combustion gas. The aim of this method is to largely enable the combustion air to be reliably and constantly conditioned even in dynamic operating conditions. To this end, an essentially constant and fully conditioned quantity of combustion gas is provided at each instant, said quantity corresponding to at least the maximum quantity required by the respective internal combustion engine. The invention also relates to a method for determining the quantities of pollutants in the exhaust gases of an internal combustion engine by diluting the exhaust gases using a diluent gas of a known composition. In order to enable the exhaust gases to be diluted in a precisely defined manner, and thus to precisely determine the quantities of pollutants, simply and reliably, an essentially constant and fully conditioned quantity of humidity and/or temperature-conditioned combustion gas is supplied at each instant, said quantity corresponding to at least the maximum quantity required by the respective internal combustion engine, and the exhaust gases are diluted with the quantity of combustion gas which is not used by the internal combustion engine. The invention also relates to devices for carrying out the two methods cited, each comprising a supply line (15) to the internal combustion engine (1), for the humidity and/or temperature-conditioned combustion gas, at least one measuring point (30) for determining the concentration of pollutants, and a determination device (32, 33; 41, 42) for the flow of a gas, said determination device comprising a passage (15) for a diluent gas of a known composition. Said devices are characterised in that the supply line or supply passage (15) is designed for at least the maximum quantity of combustion gas required by the respective internal combustion engine (1), and a suction pipe (2) which can be connected to the internal combustion engine (1) branches off from said supply line (15).