Abstract: A portable exhaust hood isolates sections of piping for maintenance and repair. It has a transparent front panel to provide a clear viewing shield, which can be adjusted between open and closed positions. The use of a collapsible frame within an enclosure made of flexible material contributes significantly to the convenience and portability of the hood, and its relatively inexpensive construction permits disposal, as need be, without substantial economic detriment.

Abstract: An environmental control hood assembly includes a headpiece and a noise filter subassembly which is disposed within the headpiece adjacent its top wall. The filter subassembly includes a silencer member with an air-permeable wall portion and is connected to the conduit which in turn is connected to the source of air under pressure. The silencer member in turn is disposed within a foam member which is fabricated of an air-permeable synthetic resin open cell foam so that air introduced into the silencer member must travel a path through the silencer member and through the foam with resultant reduction in the sound level of that air. A barrier may be provided under the silencer to preclude direct flow of air from the silencer downwardly through the foam, and the filter subassembly may include a bottom sheet of an air-pervious material.