stovepipes

/S T OW1 V P AY0 P S/
noun
  1. 1

    Sheet-metal tubing used as a chimney for a stove or furnace.

  2. 2

    A channel for information which is compartmentalized in such a manner that some parties who might be interested in its use or be able to utilize it are restricted from accessing it.

Source: https://en.wiktionary.org/wiki/stovepipe, https://en.wiktionary.org/wiki/stovepipes