An apparatus for the collection of samples of exhaled air during normal respiration, comprising a flow generator, an orally insertable exhalation air receiver, and a device for isolating the nasal airways, wherein the apparatus further comprises: a sensor for detecting a change in a parameter representing the change from inhalation to exhalation and to transmit said change as a signal a control unit adapted to receive said signal and to control said device for isolating the nasal airways wherein the flow generator is connected to or integrated with the exhalation air receiver. A method of collecting samples of exhaled air during normal respiration conditions, comprising the steps of: detecting a change in a parameter representing the change from inhalation to exhalation and transmitting said change as a signal receiving said signal in a control unit activating a device for isolating the nasal airways activating a flow generator connected to an exhalation air receiver and collecting a sample of exhaled air during exhalation when the nasal airways are isolated.
