Which statement best describes the outcome of a collocation comparison with a reference monitor?

• A. It helps verify the geographic location of the monitor.
• B. It quantifies instrument bias by comparing readings with a reference monitor.
• C. It replaces the need for QA/QC documentation.
• D. It only checks data recording speed.

Answer: (B)

Collocation comparison with a reference monitor is about measuring how an instrument stacks up against a trusted standard. By running both instruments side by side under the same air conditions, you directly compare their readings to see how far the instrument deviates from the reference. That difference reveals instrument bias, a systematic error that can indicate drift or calibration needs. Knowing the bias lets you adjust or apply correction factors and supports QA/QC by showing that measurements are accurate and traceable to the standard.

This isn’t about locating the monitor geographically, nor about replacing QA/QC documentation, and it doesn’t assess how fast data are recorded.