What is the impact of sensor calibration on CO2 monitoring?

• A. Calibration eliminates all measurement errors.
• B. Calibration can introduce errors, typically ±50 ppm at rated temperature.
• C. Calibration doubles the outdoor air requirement.
• D. Calibration reduces sensor life.

Answer: (B)

Calibration adjusts the sensor so its readings align with a known reference, reducing bias, but it does not eliminate all measurement errors. In CO2 monitoring, sensors drift over time due to aging, environmental factors, and sensor nonlinearity, so even after calibration there remains some uncertainty. That residual accuracy is typically on the order of plus or minus about 50 ppm at the rated temperature. Calibration can itself introduce small uncertainty if the calibration gas, procedure, or conditions aren’t perfect, or if the sensor experiences temperature/humidity changes that aren’t fully compensated. So readings after calibration are more accurate than uncalibrated ones, but they’re not perfect, and you’ll still see some variation around the true CO2 concentration. The other statements aren’t correct: calibration doesn’t eliminate all errors, doesn’t inherently double outdoor air requirements, and doesn’t normally shorten sensor life.