2006 New York Code - Gas Equipment Connected To Chimneys.

 
    § 27-883 Gas equipment connected to chimneys. Automatically controlled
  gas-fired  equipment  connected  to a chimney that also serves equipment
  for the combustion of solid or liquid fuel shall  be  equipped  with  an
  automatic  pilot.  A  gas-fired  equipment  vent connector and a chimney
  connector from equipment burning  another  fuel,  located  on  the  same
  floor, may be connected into the same chimney through separate openings,
  or  may  be  connected  through a single opening if joined by a suitable
  fitting located as close as practicable to the chimney. If two  or  more
  openings  are  provided  into  one  chimney,  they shall be at different
  levels.