 The planned non-commercial study is a randomised, controlled crossover trial of ambulatory oxygen against no ambulatory oxygen over a four week period two weeks on ambulatory oxygen and two weeks on air, with no portable devices, to evaluate the effects of ambulatory oxygen on health status in patients with ILD. A short crossover study in this context has many advantages, since ambulatory oxygen has immediate effect, with no wash-out period needed after use. The primary outcome of the study will be the change in health status, as measured by the K-BILD questionnaire Thorax 2012 67: 804-810. 