Vapour pressure is an important physical parameter which must be monitored in the manufacture and use of many fluids. It is defined as the pressure at which a liquid and its vapour are in equilibrium at a definite temperature.
Vapour pressure is critical to quality control and the performance of both automobile and aviation gasolines. It affects start up, warm up, tendency to vapour lock and provides an indirect measure of potential emission levels. Vapour pressure affects the drying time of solvent-based products and is often important in identifying potential safety characteristics when a liquid, such as crude oil, is stored or transported