Abstract: On May 31, 1996, Employees #1 through #3 were using a propane slab saw to cut holes in a concrete floor in preparation for installing electrical boxes. The employer had enclosed the room to contain the dust, but the excessive amount of dust generated during the process obstructed the flow of air through the air filter of the saw. The saw began to run rich and produced an excessive amount of carbon monoxide from incomplete combustion of the engine. Employees #1 through #3 suffered from carbon monoxide poisoning. Employee #1 was admitted to the hospital, where tests revealed a blood carboxyhemoglobin level of 20. Employees #2 and #3 had levels between 12 and 13; they were treated at the hospital and released.