Peroxidizable materials can form peroxides in storage, generally when in contact with the air. These peroxides present their most serious risk when the peroxide-contaminated material is heated or distilled, but they may also be sensitive to mechanical shock. The quantity of peroxides in a sample may be determined using a simple peroxide test strip. A short list of some of the most common chemicals which are prone to the formation of peroxides in storage is available here.