What is "unvented"

Usage examples of "unvented".

But I still have a problem with closets and other small, unvented dark areas because of him.

Impervious to hunger, he was possessed of such a quantity of unvented vigor that he longed to leap into the river and race the boat to Boquichicos.

Its vaulted ceiling was black with the soot from centuries of unvented cooking fires, its ancient murals obscured by grease.

Sick with cynicism and unvented rage, a shelled self thrilled only by mastery, power games, control, armor-plate with a wounded beast inside?