During exhalation, there is continuous flow of gas, allowing the patient to breathe from the circuit rather than open a demand valve. A demand flow ventilator refers to a ventilator that allows inspiratory flow of gas to the patient between ventilator breaths through a demand valve that is opened by the patient’s inspiratory efforts.
During exhalations, when sufficient positive air pressure is achieved, the membrane lifts and the wearer’s unfiltered breath exhausts (exits) from the valve, with only a portion of the exhaled breath from the wearer passing back through the filter media.
