An inlet and/or outlet air hood comprising vertical storm louvers is provided that is particularly well suited for use on a Mobile Offshore Drilling Unit and other marine vessels, although its use is not so limited. The hood may comprise a basic cube shape, which affords a smaller projected footprint than conventional round- or mushroom-shaped hoods and may incorporate an internal flow shaper, such as an inlet/outlet bell, to reduce airflow resistance. In addition, the hood may be configured to incorporate an internal valve or baffle to create a watertight closure.