The tradition of ringing a bell at a firefighter's funeral stretches back more than 200 years.
Generations ago, a bell would ring at the beginning and end of a shift and to alert firefighters of an emergency. After the call, when the emergency was over, the bell would again ring.
At the funeral, the ringing of the bell is symbolic. According to the IAFF protocol: "The ringing of the bell represents the end of the emergency and the return to quarters, and is usually three rings of the bell, three times."
As made famous in the movie Backdraft, the Chicago Fire Department rings out the alarm code 3-3-5 — signifying the company has returned home to quarters.