For example, benzoyl peroxide which is a solid at room temperature, can ignite or explode from heat, impact or friction must be kept moist on storage. The unscrewing of a lid covered with the dry chemical can set off the entire lot. For a chemical R-H, the chain may be initiated by ultraviolet light, by the presence of a radical source, and by the peroxide itself. The reaction can be initiated by light or by a contaminant. Peroxide crystals may form even on the threads of a sealing plug or cap.
Ethers are the most notorious peroxide formers.
Table 2 lists groups of peroxidizable organic chemicals in order of decreasing hazard. However, not all chemicals which fall into these categories have been shown to form potentially dangerous peroxides. MSDS or other chemical literature for hazard potential of individual chemicals should be consulted. Peroxidation is generally a problem of the liquid state. Solid peroxide formers present little problem except when finely divided because the reaction, if any occurs only at the surface.