To evaluate the usefulness of a new oxymatic conserver, Demand Oxygen Delivery System (DODS), we compared DODS breathing with Standard steady flow (SF) breathing in thirteen subjects with chronic respiratory failure due to mainly tuberculosis sequelae. The value of the DODS (Oxymatic) is that it delivers oxygen only during early inspiration, so as to minimize loss from delivery during expiratory phase. Improvement of SaO2, measured by BIOX 3740, and PaO2 were observed at rest and on exercise. The oxygen consumption ratio of the DODS to the SF method was between 0.5 and 0.3, favoring the DODS over the SF method. In some patients DODS hardly ran at rest. But no problems are observed during exercise. The results indicate the effectiveness of DODS in advancement of quality of life patients with chronic respiratory failure.