2006 New York Code - Chief May Be Designated As Commissioner.

 
    §  482.    Chief  may  be  designated as commissioner.   The mayor may
  designate the chief of the fire department to serve as commissioner, and
  in such case he shall exercise the powers and duties of commissioner and
  shall continue to exercise his powers and  duties  as  chief  and  shall
  receive  the  salary of the commissioner.  While serving as commissioner
  the chief shall forfeit none of his pension  rights  and  privileges  as
  chief  or his civil service status, and such service and the time during
  which he so serves shall be part of his time and service as chief.  Such
  designation as commissioner shall be in writing filed in the  office  of
  the department and in the office of the mayor.