Why is collocation important in QA/QC for ambient air monitoring?

• A. It reduces the cost of monitoring by sharing equipment.
• B. It ensures there is enough sampling capacity to collect data during storms.
• C. It allows the lead field technician to train new staff more effectively.
• D. It provides a basis to assess bias and precision by running two monitors side-by-side, ensuring data quality for regulatory use.

Answer: (D)

Collocation means placing two or more monitors side-by-side and comparing their readings. This setup lets you directly assess how closely the instruments agree, which reveals bias (a systematic difference between instruments) and precision (the random variability between them). Because ambient air monitoring data are used for regulatory decisions, establishing that monitors produce consistent and accurate results is essential. Collocation provides the real-world evidence needed to validate instruments, detect calibration drift or inter-instrument differences, and apply any necessary corrections. While sharing equipment, handling storm sampling, or training staff aren’t the primary goals, they don’t directly establish data quality for regulatory use the way parallel measurements do.