To prevent partial saturation of a getter by contact with absorbable atmospheric gases when the getter is introduced into a vacuum vessel, a method for introducing and activating the getter and a getter unit includes introducing the getter into the vacuum vessel packaged in a protective sleeve, closing off the vacuum vessel, evacuating the vessel, and opening the protective sleeve only after the evacuation has commenced. The protective sleeve can be opened by the sleeve being made to burst under the action of a protective gas atmosphere that is present.