What does a "P" next to a substance in the ERG signify?

A "P" next to a substance in the Emergency Response Guidebook (ERG) indicates that the substance has polymerization potential. Polymerization refers to a chemical reaction in which small molecules, known as monomers, combine to form larger, more complex structures called polymers. Substances that can undergo polymerization may be hazardous, particularly if the reaction is uncontrolled, as it can lead to the release of heat, pressure build-up, and, in some cases, explosions.

Understanding the presence of "P" in the ERG is crucial because it enables responders to take appropriate precautions when dealing with these substances. Being aware that a substance can polymerize allows responders to assess the risks involved and implement safety measures, such as minimizing heat exposure or using appropriate containment methods. This type of knowledge is essential for effectively responding to incidents involving hazardous materials.