Colorado Air Monitoring Specialist Practice Test

Calibration drift occurs when an instrument’s readings gradually move away from true concentrations. Detecting this drift relies on ongoing checks that verify the instrument’s response against known references.

Regular zero and span checks are essential: a zero check confirms the baseline output when the target pollutant is absent, and a span check confirms the sensor’s response across its measurement range using a known calibration standard. These checks catch shifts in the instrument’s baseline or its overall sensitivity.

Calibration gas responses provide a direct test of the instrument’s accuracy at specific, known concentrations. By pushing the sensor with recognized gas concentrations, you verify that the instrument’s scaling remains correct and that there isn’t an unexpected change in sensitivity.

Drift is monitored over time by comparing the instrument’s data with collocated reference measurements or data from a trusted nearby monitor. This collocation data reveals biases or gradual deviations that may not be evident from a single check, helping to separate instrument drift from natural concentration variability.

When drift is detected, corrections are applied to the data or the instrument is recalibrated, and records are updated to reflect the adjustment. Data affected by drift may be flagged or excluded if the drift cannot be adequately corrected.

This approach ensures drift is identified and addressed through routine, independent verification rather than relying solely on initial installation checks, manufacturer logs, or assuming data are correct if they look consistent.