A syringe, comprising: a first sleeve having an opening end and an engaging end, the opening end of the first sleeve having a sleeve opening; a sleeve piston having two ends with one end thereof having a protrusion, two ends of the sleeve piston being communicated with each other via at least one through hole, the sleeve piston being disposed in the first sleeve to be movable, the other one end of the sleeve piston without the protrusion facing toward the opening of the first sleeve and being spaced from the opening of the first sleeve with a distance; a second sleeve having a closed end and an opening end being opposite to the closed end; wherein the second sleeve has a sleeve inner tube, wherein, the sleeve inner tube has an end which is connected to the closed end of the second sleeve; wherein there is a gap between a peripheral wall of the sleeve inner tube and a peripheral wall of the second sleeve; wherein the gap is all around the sleeve inner tube due to the coaxial arrangement between the sleeve inner tube and the second sleeve; wherein the length of the sleeve inner tube is smaller than the length of the second sleeve; characterized in that provided that when a pressure vessel containing a fluid and sealed by a vessel lid is positioned inside the sleeve inner tube and when the first sleeve is assembled with the second sleeve and the protrusion pierces the vessel lid, a peripheral wall of the first sleeve inserts into the gap between the peripheral wall of the sleeve inner tube and the peripheral wall of the second sleeve while the pressure vessel is pushed forward against the sleeve piston; whereby the peripheral walls of the first sleeve, the sleeve inner tube, and the second sleeve are configured to be assembled to form a triple-layer configuration; wherein when the protrusion pierces the vessel lid, the fluid inside the pressure vessel flows into a first accommodating space in the first sleeve through the vessel opening and the at least one through-hole. a first sleeve having an opening end and an engaging end, the opening end of the first sleeve having a sleeve opening; a sleeve piston having two ends with one end thereof having a protrusion, two ends of the sleeve piston being communicated with each other via at least one through hole, the sleeve piston being disposed in the first sleeve to be movable, the other one end of the sleeve piston without the protrusion facing toward the opening of the first sleeve and being spaced from the opening of the first sleeve with a distance; a second sleeve having a closed end and an opening end being opposite to the closed end; wherein the second sleeve has a sleeve inner tube, wherein, the sleeve inner tube has an end which is connected to the closed end of the second sleeve; wherein there is a gap between a peripheral wall of the sleeve inner tube and a peripheral wall of the second sleeve; wherein the gap is all around the sleeve inner tube due to the coaxial arrangement between the sleeve inner tube and the second sleeve; wherein the length of the sleeve inner tube is smaller than the length of the second sleeve; characterized in that provided that when a pressure vessel containing a fluid and sealed by a vessel lid is positioned inside the sleeve inner tube and when the first sleeve is assembled with the second sleeve and the protrusion pierces the vessel lid, a peripheral wall of the first sleeve inserts into the gap between the peripheral wall of the sleeve inner tube and the peripheral wall of the second sleeve while the pressure vessel is pushed forward against the sleeve piston; whereby the peripheral walls of the first sleeve, the sleeve inner tube, and the second sleeve are configured to be assembled to form a triple-layer configuration; wherein when the protrusion pierces the vessel lid, the fluid inside the pressure vessel flows into a first accommodating space in the first sleeve through the vessel opening and the at least one through-hole.