With the widespread use of non-invasive positive pressure mechanical ventilation, great efforts have been made to produce machines, the bi-level home ventilators, which are less sophisticated, cheaper and able to better compensate air leaks with respect to the domiciliary volume-target machines and the traditional ventilators used in intensive care unit. As consequence of quick technologic evolution, bi-level home ventilators may be nowadays successfully applied for both the non-invasive ventilatory domiciliary treatment of chronic respiratory failure and the management of acute respiratory failure especially outside the intensive care setting. In this paper, the author describes the technical aspects, the individual characteristics and the clinical applications of the most common used bi-level ventilators.