A method, system and device are provided for the determination of leaks in a respirator. An inspiraton pressure pinsp is recorded during an inspiration time Tinsp with a measuring device. The inspiration pressure pinsp is varied during consecutive breaths I. Leaks are determined as to leak volumes VLi from the product of pinspi and Tinspi in accordance with the equation VLi=A×pinspiB×Tinspi while the parameters A and B are determined in an analyzing unit by a regression model with pinsp as the regressor.