An exhaled breath temperature (EBT) monitor that has a synchronized two-door shutter with movable individual doors coupled with a timer in order that only a pre-determined portion of the exhalation gas stream is selected for temperature monitoring. The doors can be either in a first position, whereby the shutter passes the portion of exhaled gas direct to atmosphere with no measurement of temperature, or in a second position, whereby the shutter passes the portion of exhaled gas to a chamber for measurement of temperature by a thermal core with a temperature sensor/reader.
