An air injection apparatus is provided according to one embodiment of the present invention. The air injection apparatus includes a main body in which an air passage is formed, and an opening and closing part which is coupled to one end of the main body and in which an opening and closing protrusion having a predetermined length, protruding toward the air passage, and configured to open or close the air passage is formed on an inner surface thereof, wherein at least a part of the opening and closing protrusion may be inserted into the air passage to seal the air passage when the opening and closing part is moved in a first direction toward the main body.
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