US PATENT SUBCLASS 454 / 172
.~ Having inlet ductwork

Current as of: June, 1999
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454 /   HD   VENTILATION

168  DF  MINE {3}
172.~ Having inlet ductwork

DEFINITION

Classification: 454/172

Having inlet ductwork:

(under subclass 168) Subject matter comprising conduit structure for admitting fresh ventilating air to the ventilated space.

(1) Note. The conduit structure (ductwork) must be distinct from the walls defining the mine excavation or gallery.