Abstract: Employee #1, a mold repairer and a member of a fire brigade, responded to a fire alarm at the Cold Mill. Upon arrival at the mill, the fire brigade suppressed the fire by activating the Cardox fire suppression system. Employee #1 and another employee, both wearing a self-contained breathing apparatus (SCBA), entered the subfloor surface area to check for fire and to rescue any trapped persons. Subfloor #1 is monitored for oxygen content. At the time of entry the oxygen reading was 17.2 percent. Sublevel #2 was not monitored. The employee checked level #1, and, finding no problem, entered sublevel #2 by going down a ladder. While at level #2, Employee #1 had difficulty breathing and fell unconscious. His partner could not lift him out of the area. A local volunteer fire department (municipal) removed Employee #1 from the area, but he died. At that time, the regulator switch on the demand-pressure SCBA was noted in the don (demand) mode. Employee #1 had a heavy beard and had failed his last pulmonary function test.