BACKGROUND: During noninvasive ventilation, nonintentional leaks have a detrimental effect on the efficacy of ventilation. A wide range of industrial masks are available, with intentional leaks of different importance. The potential impact of this variability in intentional leaks on performances of bilevel ventilators has not been assessed. OBJECTIVE: To measure intentional leaks in seven different industrial masks and determine whether higher leaks modify ventilator performance and quality of ventilation. METHODS: Seven interfaces connected to four ventilators, the VPAP III ST (ResMed; NorthRyde, Australia), the BiPAP Harmony (Respironics; Monroeville, PA), the SmartAir ST (Covidien/Airox; Pau, France), and the GoodKnight 425 ST Bilevel (Covidien/Tyco-Nellcor/Puritan Bennett; Pleasanton, CA), were adapted on a mannequin connected to a lung model (ASL5000, IngMar Medical; Pittsburgh, PA). Inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure were 14 and 4 cm H(2)O, respectively. The lung model was set with a respiratory rate of 15 cycles per min and a duration of inspiration of 1 s in three simulated conditions (normal, restrictive, and obstructive). Inspiratory trigger delay and effort, capacity to achieve and maintain IPAP, expiratory cycling and tidal volume were analyzed for all masks and ventilators in the three simulated lung conditions. RESULTS: The level of intentional leaks in the seven masks ranged from 30 to 45 L/min for an IPAP of 14 cm H(2)O. Importance of leaks did not influence trigger performances. However, capacity to achieve and maintain IPAP was significantly decreased with all ventilators and in all simulated lung conditions when intentional leaks increased. This led to a maximum reduction in delivered tidal volume of 48 mL. Expiratory cycling was not affected by the level of intentional leaks except in obstructive lung conditions. CONCLUSION: Mask intentional leaks can impair efficacy of ventilation, especially when > 40 L/min.