 At the start of the trial, the effects of ambulatory oxygen on 6 Minute Walk Test 6MWT parameters will be evaluated on oxygen and on air-filled canisters, with the patient blind to the contents of the canister, to assess whether oxygen-induced improvements in 6MWT parameters can predict its effectiveness in day to day life. The 6MWT is a well established and highly reproducible test validated in ILD patients, with significant prognostic implications. 