A flow indicating system that includes a conduit that contains a substance, wherein
the conduit defines a path along which the substance primarily flows and a viewing
port attached to the conduit and the viewing port prevents substantially non-ambient
atmosphere gases and substances from escaping therefrom and allows visualization
of an internal space defined by the viewing port. A flow indicator that is positioned
within the conduit so as to be viewed via the viewing port and is positioned so
as to not to substantially interfere with a flow of the substance along the path.
