On the behalf of the Swedish Rescue Services Board (technical dept.) weapon effects on air intakes for the new type of civilian shelter "RC90" has been analysed. This report summarises data from recent years tests and calculation made by FOA. From the results, together with methods for risk analyses used by the Rescue Services Board, advises on the design of air intakes and choice of components are suggested for this and similar types of buildings. In the background material, different arrangements to reduce the air shock load on a barrier with protective valves was investigated. Hydrocode calculations and experiments with HE in a 1/4 scale model were performed as well as component tests of different valves in shock tubes with pressure loads similar to a Mk 82 bomb detonating close to the building.