Pumping device intended to be connected to a processing chamber, comprising: - a dry primary vacuum pump having: ∘ an inlet and an outlet, ∘ at least one pumping stage (10a, 10b, 10c, 10d, 10e) arranged between the inlet and the outlet, ∘ a purging means configured to inject a purging gas into said pumping stage (10a, 10b, 10c, 10d, 10e), ∘ an exhaust duct connected to the outlet, and ∘ an anti-return valve arranged in the exhaust duct, - an ejector mounted on a line bypassing the anti-return valve, the ejector comprising: - a duct having a suction orifice, an exhaust orifice, and at least one inlet nozzle (18a, 18b, 18c), and - a means for injecting motive gas for controlling the injection of a motive gas into at least one inlet nozzle (18a, 18b, 18c), characterized in that the pumping device comprises: - a first valve-comprising device connected to the purging means of the dry primary vacuum pump and intended to be connected to a gas supply, - a second valve-comprising device mounted on a line bypassing the anti-return valve upstream of the ejector, - a controlling means configured to control the first and second valve-comprising devices (5, 6) depending on an operating state of the processing chamber, the first valve-comprising device connected to the purging means also being connected to the means for injecting motive gas and being configured to switch, at least partially, the gas supply from the purging means of the dry primary vacuum pump to the means for injecting motive gas of the ejector. - a dry primary vacuum pump having: ∘ an inlet and an outlet, ∘ at least one pumping stage (10a, 10b, 10c, 10d, 10e) arranged between the inlet and the outlet, ∘ a purging means configured to inject a purging gas into said pumping stage (10a, 10b, 10c, 10d, 10e), ∘ an exhaust duct connected to the outlet, and ∘ an anti-return valve arranged in the exhaust duct, ∘ an inlet and an outlet, ∘ at least one pumping stage (10a, 10b, 10c, 10d, 10e) arranged between the inlet and the outlet, ∘ a purging means configured to inject a purging gas into said pumping stage (10a, 10b, 10c, 10d, 10e), ∘ an exhaust duct connected to the outlet, and ∘ an anti-return valve arranged in the exhaust duct, - an ejector mounted on a line bypassing the anti-return valve, the ejector comprising: - a duct having a suction orifice, an exhaust orifice, and at least one inlet nozzle (18a, 18b, 18c), and - a means for injecting motive gas for controlling the injection of a motive gas into at least one inlet nozzle (18a, 18b, 18c), - a duct having a suction orifice, an exhaust orifice, and at least one inlet nozzle (18a, 18b, 18c), and - a means for injecting motive gas for controlling the injection of a motive gas into at least one inlet nozzle (18a, 18b, 18c), - a first valve-comprising device connected to the purging means of the dry primary vacuum pump and intended to be connected to a gas supply, - a second valve-comprising device mounted on a line bypassing the anti-return valve upstream of the ejector, - a controlling means configured to control the first and second valve-comprising devices (5, 6) depending on an operating state of the processing chamber, the first valve-comprising device connected to the purging means also being connected to the means for injecting motive gas and being configured to switch, at least partially, the gas supply from the purging means of the dry primary vacuum pump to the means for injecting motive gas of the ejector.