Testing of several gases has been performed at the HIRFL Cluster Source after modifying the pumping system of the nozzle chamber and improving the conductance of the vacuum line locating between the Roots pump and the turbomolecular pump of the cluster source. To find the reasons of the nozzle blocking, we analyzed the purity of the employed gas by using Pfeiffer vacuum Quadrupole Mass Analyzer (QMA). It seemed that the purity of the gases in the tank did not meet our requirements. The partial pressure of gas is measured by QMA when hydrogen, nitrogen and argon gases were injected into the vacuum chamber Testing of several gases has been performed at the HIRFL Cluster Source after modifying the pumping system of the nozzle chamber and improving the conductance of the vacuum line locating between the Roots pump and the turbomolecular pump of the cluster source. To find the reasons of the nozzle we observed the purity of the employed gas by using Pfeiffer vacuum Quadrupole Mass Analyzer (QMA). It was that the purity of the gases in the tank did not meet our requirements. The partial pressure of gas is measured by QMA when hydrogen, nitrogen and argon gases were injected into the vacuum chamber