Controlled fixation techniques have been developed and adopted in a number of countries where chromium containing preservatives are predominantly used. The purpose of this technology is to reduce both on-site pollution and holding requirements for freshly treated timber. The fixation mechanism is complex and the time taken to complete the reaction is dependent upon a number of factors. A number of countries have proposed or introduced methods for measuring and standards for defining fixation. These are discussed in relation to the different technologies which have been commercially introduced throughout the world.