It IS a foam turret. Engines 2, 3, 4, 5 & 41 are all equipped with a CAFS (Compressed Air Foam System) designed to be used on the tunnels carrying Interstates 90 & 93 through the downtown area.
FF Sean 'Skip' Olson
Boston Fire, Ladder 14
In Memory:
FR David A. Middleton E51, LODD, Box 5247, 05/28/07
FR Paul J. Cahill E30 & FR Warren J. Payne L25, LODD, Box 4-281, 08/29/07
FLT Kevin Kelley L26, LODD, 01/09/09
FLT Edward J. Walsh E33 & FR Michael Kennedy L15, LODD, Box 9-1579, 03/26/14.
Boston Fire, Ladder 14
In Memory:
FR David A. Middleton E51, LODD, Box 5247, 05/28/07
FR Paul J. Cahill E30 & FR Warren J. Payne L25, LODD, Box 4-281, 08/29/07
FLT Kevin Kelley L26, LODD, 01/09/09
FLT Edward J. Walsh E33 & FR Michael Kennedy L15, LODD, Box 9-1579, 03/26/14.