The Lady Delia was an oil rig supply level which was being refitted by highly professional workers who understood their work and their tools but were blithely unaware of the meaning of the chemical environment in which they worked. The first clue that things were different was that the cigarettes the men were smoking burned very quickly; that seemed odd but not dangerous. Then someone threw a burning butt to the ground, and within minutes a flash fire broke out. The subsequent investigation determined that an error caused the admission of oxygen into the area, and showed at what point sufficient oxygen was present so that a cigarette could cause an explosion. As it follows the investigation, the program explains the nature of oxygen and of combustion—and of the perils of being ignorant of the basics of chemistry. (26 minutes)