The engine can pick up foam from any of the four on board foam tanks or off board from a foam pail, another rigs foam tank by going in the top or from a drum. There are two foam systems and two yellow foam pickup ports.
A bladder style foam system allows for accurate proportioning from 5 to 350 gpm of Class A or B foam in percentages from .001 to 3 percent. The system is stored on all the time, no electric pumps or flow meters, it is water powered. The other system covers the 80 to 4000 gpm flow range.
.Even with a flow of 10 gpm over 2000 gpm of foam are made each minute. Great to bury smoldering debris or cover a fuel spill during extrication.
A couple gallons of concentrate can go a long ways.
Fire attack is accomplished with CAFs or Class A foam streams then the 2 inch hose is reduced to 1" with a medium expansion tip to save everyones backs and bury smoldering ruins reducing water damage.