Over the past 5 years 16 fires have been reported to the FDA involving aluminum-bodied medical regulators. These incidents are reported to have caused severe burns to 11 health care workers and patients. Many of the incidents have occurred during emergency medical use or during routine equipment checkouts. This paper summarizes the investigation and failure analysis of several of these fires and provides the cause and origin analysis for each. Ignition with catastrophic burnout of the regulator has been observed in each of these cases. The active ignition mechanisms are felt to have included particle impact in some cases, contaminant promoted ignition in other cases, and adiabatic compression in at least one other. Several of the fires are believed to have been caused by paniculate debris entrained in the oxygen flow stream from aluminum high-pressure cylinders. The regulator design, pertaining to the exposure of aluminum to active ignition mechanisms, and the use of aluminum cylinders with aluminum regulators are discussed.