Abstract: At approximately 3:15 p.m. on December 4, 1999, Employee #1, of the Apple Valley Nursing and Rehabilitation Center in Ayer, MA, was opening an 8-liter oxygen cylinder when the regulator suddenly began to emit sparks and black soot, and then exploded. She sustained burns to her hands, but did not require hospitalization. Employee #1 was trained to perform this task, and had done so on numerous times without incident. A representative from the oxygen cylinder/regulator supplier later stated that the cause could have been a defective internal aluminum part. Additional investigation revealed that an FDA recall notice went out in 1999, warning of the dangers of oxygen cylinders made with certain internal parts composed of aluminum rather than acceptable brass construction. The part that supposedly failed was internal and was not visible from the exterior of the regulator. In a letter dated February 2, 1999, the supplier, North Atlantic Medical, assured the employer that the regulators in use complied with the FDA recall notice.