Reactive monomers are a special class of materials used widely in the chemical industry in the production of polymers. Many of these materials are thermally unstable and may polymerize during handling and storage with a release of significant amounts of energy. If this energy is not controlled properly, it can lead to a runaway reaction. Compounding the concern for the stability of monomers is the fact that these materials are typically transported and stored in large volume. The undesired initiation of the polymerization reaction may be caused by a number of factors, including contamination, exposure to extreme environmental conditions, or inhibitor loss. For example, an “unintended” polymerization can result from a seemingly benign procedure such as spill control with common absorbents. These and other factors mean that the reactive chemicals evaluation of monomers presents special problems and concerns which require more detailed experimental design for reliable hazard testing. This paper discusses the practical aspects of reactive chemicals testing strategies for monomers and rules-of-thumb for monomer inhibition, compatibility, spill control, and so-called quenching (also called short-stopping) agents. The techniques discussed range from simple “age and observe” type tests to more sophisticated heat flux calorimetry evaluations. We also discuss the more routine application of Differential Scanning Calorimetry and Accelerating Rate Calorimetry to monomers. Vent sizing applications with the VSP device are also presented with emphasis on total containment during a runaway.