VENTILATION UNIT

The ventilation unit includes: an explosion-proof valve that permits gas to flow from the inside of a housing to the outside of the housing when internal pressure within the housing is higher than external pressure outside the housing by a value larger than or equal to a predetermined value, and is capable of returning to block the flow of the gas from the inside of the housing to the outside of the housing; and a ventilation membrane that permits gas to flow between the inside and the outside of the housing even when a pressure difference between the internal pressure and the external pressure is less than the predetermined value.