hermetically sealed

Hermetically sealed means airtight—closed so completely that no air or gas can enter or escape.

The term comes from Hermes Trismegistus, a legendary figure associated with alchemy and the sealing of vessels by fusion.

Laboratory containers and food packaging may be hermetically sealed to preserve contents or prevent contamination.

Figuratively, something hermetically sealed is isolated from outside influence: He lived in a hermetically sealed world of privilege.