Publisher Summary Hazards from processes using chemicals are assessed on the basis of inherent chemical properties, chemical form, quantity, and processing conditions. Hazards can often be foreseen from basic physicochemical principles such as vapor pressure, gas-liquid solubility, liquid-to-vapor phase change, solid-to-liquid phase change, density differences of gases and vapors, density differences of liquids, immiscible liquid-liquid systems, and vapor flashing. Hazards can often be foreseen from basic physicochemical principles such as vapor pressure, gas-liquid solubility, liquid-to-vapor phase change, solid-to-liquid phase change, density differences of gases and vapors, density differences of liquids, Immiscible liquid-liquid systems, vapor flashing, effects of particle or droplet size, surface area effects in mass transfer or heterogeneous reactions, and enthalpy changes on mixing of liquids.