Alex Griff swings the sledge hammer at the red marker. With enough force, a buzzer on the simulator will sound to indicate the firefighter has broken down a door. It is one of the exercises at the Mutual Aid Box Alarm System (MABAS) center in Homewood. (Photos by Marilyn Thomas/H-F Chronicle) Start with a 50-pound weight simulating a firefighter's coat, pants, boots, gloves, airpack, mask and tools and an additional 25-pound airpack for high rise fires. Then try . . .