This paper analyses the e ects of air-structure interaction of systems subjectedto weak blast loads. While these coupling e ects are negligible for typical steel or concretestructures, they may dominate the dynamic response of lighter and more exible (compliant)systems like membranes, blast curtains or cable facades. For these light and exible systems,a classical decoupled analysis, i.e., neglecting the inuence of the surrounding air, might sig-ni cantly overestimate the deections and strains. However, we show that the coupling e ectscan be accounted for by basically adding a viscous aerodynamic damping force. We discussand compare two approaches how to obtain the aerodynamic damping term. With decreasingstructural sti ness and mass, the damping contribution of air increases signi cantly. The resultsof Hydrocode simulations are presented, and an outlook into further areas of research is given.