2006 New York Code - Draft Control.

 
    §  27-839  Draft  control.  If  a  manual  damper  or  automatic draft
  controller, is provided in the incinerator flue, it shall be capable  of
  closing off not more than ninety-five per cent of the flue area, and the
  damper  or  controller  shall  be  made  of such materials and in such a
  manner so as to  prevent  warping,  binding,  cracking,  corrosion,  and
  distortion when exposed to operating temperatures. If an automatic draft
  controller  is  used,  means  shall  be  provided  for  temporary manual
  operation.