As per API RP 571 Section 5.1.4.2 (Metal Dusting):
"Metal dusting is a type of carburization attack that typically occurs in high carbon activity environments, with temperatures generally between 900°F and 1200°F (480°C to 650°C), although damage has been reported as low as 600°F (315°C)." Therefore, the commonly accepted operational range is best described by Option A: 600°F-1200°F (315°C-
650°C).