The stability of organic peroxides is greatly reduced by contamination with materials such as strong acids or bases, sulfur compounds, amines, accelerators (promoters) or reducing agents of any type. For example, contamination of MEK peroxide with cobalt promoters can produce explosive mixtures, as can contamination of Dibenzoyl Peroxide with amine promoters. Contamination of organic peroxides with easily oxidized metals (such as copper, brass, or mild steel), metal oxides, resin sanding dust, dirt, etc. can also produce a violent decomposition. In addition, combustible materials, such as sawdust, sweeping compound, etc. in prolonged contact with organic peroxides may spontaneously ignite.