A solid particle counting system for measuring solid particle number concentrations from engine or vehicle exhausts in real-time, the system comprising: a diluter arrangement (PND1, PND2) that is configured to receive flowing gases containing solid particles and dilution gas, the diluter arrangement (PND1, PND2) is configured to mix the dilution gas with the flowing gases containing the solid particles, and the diluter arrangement (PND1, PND2) that is configured to output an output flow that is mixed gas of the dilution gas and the flowing gases containing the solid particles; a flow splitter (FS3, 200) that has an inlet that is configured to receive the output flow from the diluter arrangement (PND1, PND2) and has two outlets , the flow splitter (FS3, 200) is configured to split the output flow outputted from the diluter arrangement (PND1, PND2) into two flows that outflow from the outlets ; a condensation particle counter that includes work fluid and is connected to one of the outlets of the flow splitter (FS3, 200), the condensation particle counter is configured to measure solid particle number concentration of flow received from the flow splitter (FS3, 200), a vacuum pump that is connected to another outlet of the flow splitter (FS3, 200) that is different from the outlet connected to the condensation particle counter ; a first flow route from the outlet of the flow splitter (FS3, 200) to the condensation particle counter ; and a second flow route from atmosphere to the condensation particle counter via confluence on the first flow route, the second flow route including a valve arrangement (SV, V3) arranged such that opening the valve arrangement (SV, VR) during the starting of the vacuum pump reduces a pressure pulse at the condensation particle counter caused by the starting of the vacuum pump , thereby avoiding the work fluid backflow from the condensation particle counter . a diluter arrangement (PND1, PND2) that is configured to receive flowing gases containing solid particles and dilution gas, the diluter arrangement (PND1, PND2) is configured to mix the dilution gas with the flowing gases containing the solid particles, and the diluter arrangement (PND1, PND2) that is configured to output an output flow that is mixed gas of the dilution gas and the flowing gases containing the solid particles; a flow splitter (FS3, 200) that has an inlet that is configured to receive the output flow from the diluter arrangement (PND1, PND2) and has two outlets , the flow splitter (FS3, 200) is configured to split the output flow outputted from the diluter arrangement (PND1, PND2) into two flows that outflow from the outlets ; a condensation particle counter that includes work fluid and is connected to one of the outlets of the flow splitter (FS3, 200), the condensation particle counter is configured to measure solid particle number concentration of flow received from the flow splitter (FS3, 200), a vacuum pump that is connected to another outlet of the flow splitter (FS3, 200) that is different from the outlet connected to the condensation particle counter ; a first flow route from the outlet of the flow splitter (FS3, 200) to the condensation particle counter ; and a second flow route from atmosphere to the condensation particle counter via confluence on the first flow route, the second flow route including a valve arrangement (SV, V3) arranged such that opening the valve arrangement (SV, VR) during the starting of the vacuum pump reduces a pressure pulse at the condensation particle counter caused by the starting of the vacuum pump , thereby avoiding the work fluid backflow from the condensation particle counter . <EOS>