Although ISO 13943 defines flashover as "transition to a state of total surface involvement in a fire of combustible materials within an enclosure", a broad definition that embraces several different scenarios, including backdrafts, there is nevertheless considerable disagreement regarding whether or not backdrafts should be properly considered flashovers. The most common use of the term flashover is to describe the near-simultaneous ignition of material caused by heat attaining the autoignition temperature of the combustible material and gases in an enclosure. Flashovers of this type are not backdrafts as they are caused by thermal change. Backdrafts are caused by the introduction of oxygen into an enclosed space with conditions already suitable for ignition, and are thus caused by chemical change.