N.Y.C. Admin. Code § 27-876: § 27-876 Chimneys for building service incinerators.

Chimneys for building service incinerators shall be constructed in accordance with the requirements of this subchapter for high or medium temperature chimneys, based upon the temperature of the flue gases leaving the equipment, except that no reduction of flue gas temperature shall be recognized if such reduction is the result of using water scrubbers or barometric dampers. In addition, such chimneys shall comply with the following:

(a) Chimneys shall extend through the roof and be open to the air.

(b) Chimneys shall be provided with a spark arrester as required in paragraph four of subdivision (a) of section 27-875 of this article.

(c) Incinerators may discharge into chimneys serving other equipment provided such combined chimney is of adequate size for both uses, conforms to construction required for the highest temperature, and adequate draft control equipment is provided for each device connected to the combined chimney.