evidence: Face masks are a first-line defence against the COVID-19 pandemic.1 Concerns about face masks reducing oxygen saturation (SpO2) have been negated by controlled studies in healthy individuals.2 3 Universal masking must be followed without exceptions. However, persons with pre-existing cardiorespiratory diseases like interstitial lung diseases (ILD) have limited functional reserves. We explored the effects of face masks in patients with connective tissue disease (CTD)-associated ILD (CTD-ILD). Patients between 18 and 75 years of age with high-resolution CT (HRCT)-proven CTD-ILD and with Medical Research Council scale grades 1–3 dyspnoea and forced vital capacity (FVC) of less than 70% were included in this crossover trial. If FVC was >70%, patients were included only if the extent of involvement on HRCT was more than 20% of the lung. Patients requiring oxygen supplementation and with myositis or lower limb pain were excluded. Initial SpO2 was recorded and a standard 6 min walk test (6MWT) was carried out with and then without a standard three-layer surgical face mask. Adequate precautions were taken to prevent the spread of COVID-19 during the tests. Distance covered during the 6MWT was the primary outcome measure. The secondary outcome measures …