US PATENT SUBCLASS 454 / 46
.~.~ Pressurized air lining

Current as of: June, 1999
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454 /   HD   VENTILATION

1  DF  CHIMNEY OR STACK {6}
44  DF  .~ Having lining or sleeve {3}
46.~.~ Pressurized air lining

DEFINITION

Classification: 454/46

Pressurized air lining:

(under subclass 44) Subject matter comprising a layer of air which encases the vertical conduit section, the layer of air having a pressure above ambient.