Book excerpt: Perfume Engineering is a must-have reference for engineers who design any products that require fragrances, such as perfumes, cosmetics, healthcare and cleaning products. This book provides the reader with practical guidance on perfume design, performance and classification, from its beginnings as a liquid mixture to the vapour phase, by way of odorant dispersion and olfactory perception. It does this through the application of development and validation models to account for fragrance evaporation, propagation and perception.