The Open Air School Movement was a major public health initiative created within the Western World in the first half of the 20th century. Open air nursery and primary schools were introduced in the first decade of the century throughout Europe and North America and over the next 20-30 years became numerous and widespread. This paper examines the influences behind the Open Air school movement predating the influential School opened in Charlottenberg, Germany in 1904 and the working philosophy of these schools both in relation to health and more generally. It also documents the day to day working practices of the schools, their changing role as they were affected by changes in treatment and prevention of infectious disease and their subsequent decline and closure after the 2nd world war. The School movement is examined in the context of a more general social health agenda with particular emphasis on the ideas of “fresh air “ providing a desirable and healthy environment as a method of ( particularly ) control and prevention of TB – and the belief and investment in a concept in the absence of evidence of real benefit.