If dissolved oxygen is a critical parameter, EPA New England recommends a second calibration point using the zero DO solution or a check of low DO accuracy with a zero DO solution.
You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.-
QA Bulletin: Calibration of Dissolved Oxygen Meters: February 2006 (PDF)(3 pp, 10 K)
If dissolved oxygen is a critical parameter, EPA New England recommends a second calibration point using the zero DO solution or a check of low DO accuracy with a zero DO solution.