The acute toxicity of nickel carbonyl by inhalation is high. Acute toxic effects occur in two stages, immediate and delayed.
Recovery is protracted and characterized by fatigue on slight exertion.
Nickel carbonyl is not regarded as having adequate warning properties. Repeated or prolonged exposure to nickel carbonyl has been associated with an increased incidence of cancer of the lungs and sinuses. Carbon dioxide, water, or dry chemical extinguishers should be used for nickel carbonyl fires. In the presence of air, nickel carbonyl forms a deposit that becomes peroxidized and may ignite. Nickel carbonyl is incompatible with mercury, nitric acid, chlorine, and other oxidizers, which may cause fires and explosions.