The aerosol diluting apparatus includes

a first diluting unit to provide a first modified sample flow by combining an aerosol sample flow with a first diluting gas flow,
an ejector unit to draw the first modified sample flow from the first diluting unit to the ejector unit and to provide a second modified sample flow by mixing a second dilution gas flow with the first modified sample flow,
a control unit, and
a control valve,
wherein the control unit and the control valve are arranged to adjust flow rate of the second dilution gas flow according to an inlet pressure of the aerosol sample flow, so as to keep the dilution factor of the diluting apparatus substantially independent of the inlet pressure.