Carbonaceous gases can cause carburization, metal dusting and coking on metals and alloys. The mechanisms and kinetics of these phenomena are described for iron and steels, nickel and Ni-base alloys, and ways and means for their prevention are pointed out. The carbon transfer to the metal phase, necessary for these phenomena can be impeded by sulfur adsorbed from the atmosphere and the metal dusting mechanism on iron and steels can be interrupted by sulfur. Also protective Cr-rich oxide scales can hinder or even suppress carbon transfer and in this way the deleterious phenomena. Too high temperatures (> 1050 degreesC) must be avoided since the scales may fail by conversion to carbides. At lower temperatures (< 650 degreesC) protective scales may not be formed due to too slow Cr-diffusion and their formation must be fostered by providing fast diffusion paths.