Mushroom vents are a common feature in campervans and motorhomes. They are usually mounted in the roof and allow for ventilation, air circulation and air exchange.
Campervan Mushroom Vents
Mushroom vents are designed to help keep the interior of your campervan cool in summer and prevent condensation during winter months. They work by allowing warm air to escape while drawing in fresh air from outside.

The vents are available in a variety of styles, including dome, low-profile, and louvered.