Chief of Department is on continuous duty from 0900 Monday morning to 1700 hours Friday evening. There are ( or were when I was on the staff) 3 four star chiefs (Chief of Operations, Chief of Fire Prevention and Chief of Support Services) and 1 three star chief (The Assistant Chief of Operations) who would rotate as Acting Chief of Department from 1700 Friday to 0900 Monday. Have the duty one weekend and then off the next three. If I remember right (been 30 years) the COD had mandatory response to 4 alarms fires, death of member, as directed by the Fire Commissioner and any incident that may reflect negatively on the department. Of course the COD could respond to any incident large of small as he felt like it. I had this acting COD duty for over a year as Assistant Chief of Operations and then as Chief of Fire Prevention.
Borough Chiefs had mandatory response, in their borough, to 10-76 fires, death of member, 3 or more 10-45's, 3 alarm incidents, possible negative incidents and as directed by Chief of Operations, COD and/or Fire Commissioner. As Deputy Borough Commander Manhattan and later as Borough Commander Manhattan with at times 3 staff chiefs working the tour in the Borough we would respond as directed by the Borough Commander. The only times I can remember more than one of the Manhattan staff chief responding was two fires in the Empire State Building, one 2nd alarm and one went to a 4th.
I was on the staff from 1984 to 1991. Probably much of what I have typed above is no longer the practice. I enjoyed the staff as I got to work with the best man I ever worked with Matty Farrell who was the Manhattan Borough Commander when I was Deputy Borough Commander and whose place I took when he retired in 1989.