CareFusion MicroCO Meter Manuel D'utilisation page 20

The display reading will rise to a plateau over the course of a several
seconds. The final value will be held until the unit is turned off and
represents parts per million CO or %COHb depending on the slide
switch position.
The lights will come on according to the table on page 12 and the red
light will flash and an alarm will sound if the measurement rises above
72ppm (12%COHb).
If this occurs then the possibility of CO poisoning should be
investigated as this level of CO is unlikely to be produced by cigarette
smoking.
Important note:
Before repeating a measurement the unit must be turned off,
and the mouthpiece and adapter removed for at least 1 minute.
This is to allow re-equilibration with ambient air and to dry the
surface of the sensor. Visually inspect that all moisture has
evaporated from the surface of the sensor before reuse.
If the unit is switched on again too quickly after use there may be a
response to residual expired carbon monoxide from the previous test.
In this case the display will show:
If this is displayed then turn the unit off, remove the mouthpiece
adapter, and expose to ambient air for 2 minutes before repeating the
test.
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