Welch Allyn CP 150 spirometry option - User Manual - Manual (Page 27)

The results display for a single-flow calibration after no air has moved for three
seconds.
10. Review the results.
Note Check the error percentages for the expired and inspired
volumes. Both volumes must be less than ±3.5% for the
calibration to be acceptable. For single-flow calibrations, the
measured and adjusted curves should match.
Note The syringe used to check the volume calibration of
spirometers must have an accuracy of 15 mL for a 3-L
syringe.
11. Touch the Accept button to save the calibration results.
Directions for use About calibration 23