Abstract: A cable suspended hermetic structure having a floor and walls combining with the undersurface of superstructure substructure such as a bridge forming an enclosure defining a workspace wherein one or more persons having access to the bridge substructure can work to repair and maintain said structure while containing the debris derived from said work within the enclosed structure and where applicable an external source of filtering air can be connected to the interior of the enclosure without comprising the hermetic nature of the enclosure.