The whole point of Thermos is to keep things warm for a long time. That means pressure. It's a basic safety feature.

> The whole point of Thermos is to keep things warm for a long time. That means pressure.

That by far is not enough to forcefully yeet out the cap, probably not even if you take it to an Antarctic research base in -40 °C outdoor weather.

People forgetting about content that ferments however? Kaboom.

	▲	globular-toast 4 hours ago \| parent [-]
		On a planet where fermentation exists, such as planet Earth, the only planet on which we, humans, reside and therefore where these containers are made and used, that means pressure. Happy now?