Ventilation Member, Ventilation Member Kit, and Vented Housing and Vented Tank Using Them

A ventilation member and a ventilation member kit are provided that can extend the time until fogging will be produced in a housing and also can shorten the time until the produced fogging will be cleared up even when the interior of the housing has been fogged. A vented housing and a vented tank using them are also provided. A ventilation member includes: a first gas permeable membrane, a second gas permeable membrane, and an absorbing layer allowing a gas passing through an opening of a housing or a tank to permeate therethrough, with the ventilation member being fixed to the opening; a support body for supporting the first gas permeable membrane, the second gas permeable membrane, and the absorbing layer; and a first one-way valve disposed so as to cover the first gas permeable membrane. The first gas permeable membrane and the second gas permeable membrane are disposed in such a manner that the gas permeates through the gas permeable membranes independently of each other. The second gas permeable membrane and the absorbing layer are disposed in such a manner that the gas permeates through the second gas permeable membrane and the absorbing layer successively. The absorbing layer contains a water absorbent.