Sweep...

The Chimney Sweep

A chimney uses the pressure difference caused by a hot column of gas to create a draught and draw air over the hot coals or wood enabling continued combustion. Chimneys may be straight or contain many changes of direction. During normal operation, a layer of creosote builds up on the inside of the chimney restricting the flow. The creosote can also catch fire, setting the chimney and the building alight. The chimney must be swept to remove the soot. This was done by the master sweep and his apprentices.

Wellerschimneysweeps.com

With the increased urban population that came with the Age of Industrialization, the number of houses with chimneys grew apace. Buildings were higher and the new chimneys tops were grouped together.  The routes of flues from individual grates could involve two or more right angles, horizontal angled and vertical sections, They were narrow to create a better draught- 14in by 9in being a common standard.  Chimney sweeping was one of the most difficult, hazardous, and low-paying occupations of the era, and consequently has been derided in verse, ballad and pantomime.

Wikipedia.org