An iso-kinetic probe for the analysis of the pollution of the gases generated by an aircraft engine is disclosed. The probe includes an air tapping tube having an upstream end inserted into a conduit wherein a gas stream flows and a gas stream inlet velocity adjustment device provided at an orifice of the tapping tube. The tube has a downstream end mounted in a fixed manner on a base. The base has an outer diameter mounted in an inner diameter d of a passage bushing. The inner diameter d of the passage bushing being sufficiently great so that the upstream end of the tube is suitable to fit through the inner diameter of the passage bushing. The probe also includes a measurement chamber having an end connected to the base.