What are zero and span checks and why are they performed?

• A. They are checks to ensure data is stored in the correct file format.
• B. Zero checks verify no baseline signal, span checks verify response to a known calibration gas; both ensure measurement accuracy.
• C. They are weather-related checks for solar radiation.
• D. They measure the humidity inside the enclosure.

Answer: (B)

Zero and span checks are calibration steps that verify an instrument’s readings are accurate. A zero check ensures the instrument shows no baseline signal when exposed to clean air (no target gas), checking for drift or offset in the detector. A span check then uses a known calibration gas to confirm the instrument’s response at a defined concentration, ensuring the full-scale response and linearity are correct. Together, they help maintain measurement accuracy, detect sensor aging or environmental effects, and support reliable data. They’re not about file formats, weather conditions, or humidity inside the enclosure.