That's it. Emergency venting.

She cools his domain with Spring air, venting heat up to the surface, creating summer.

Burets are used to titrate liquids. A buret is filled with a specific volume of a liquid, and placed beneath it is a container such as an Erlenmeyer flask. By opening the valve on the buret, the liquid in the container will then be titrated. High quality burets have a venting mechanism with which they can be very easily refilled with the exact volume for which the buret is calibrated.