"In the US, the minimal risk level of nickel and its compounds is set to 0.2 µg/m3 for inhalation during 15 364 days.[62] Nickel sulfide fume and dust are believed carcinogenic, and various other nickel compounds may be as well.[63][64] Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of the metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception; nickel carbonyl is also explosive in air. ... Sensitized individuals may show an allergy to nickel affecting their skin, also known as dermatitis."