Deaerators may be considered as the most versatile class of textile auxiliaries useful for nearly each kind of wet processing and make up of textile goods. Hardly anybody is aware of the multiple purposes a deaerator is useful for in order to optimize efficiency and operational safety during manufacturing of textiles. The article describes: - properties of deaerating agents, - differences between wetting agents, defoamers and deaerators, - fields of applications for deaerators, - manufacturing of deaerators, - types of deaerators, their history and properties, - 2nd generation of deaerators with silicone peak.