The chimney shaft should be placed in close proximity to the furnace, the internal measurements, at the base, being at least 2 feet square, and should be carried up to a height of 60 feet, though for the Carbon Oxide Company's furnace 50 feet is sufficient. The chimneys at Hull and Ilford are 70 feet, while the one at Birmingham is 80 feet high. It will be found from a study of the crematoria throughout the world that only in England is the chimney clothed with a tower; abroad, no pretence is made to hide its true purpose.

It is necessary to provide, at the base of the shaft, a pilot fire to warm the flue and assist the furnace when lighting up, consisting of a small fire grate, or, better still, a series of bunsen burners.