What limits interference during fresh air calibration?

• A. Charcoal filters
• B. Metal shielding
• C. Silicone membranes
• D. Electrical grounding

Answer: (A)

During fresh air calibration, the aim is to establish a clean reference air by removing background interferents that can skew the sensor’s baseline. Activated charcoal acts as a chemical filter, adsorbing a wide range of volatile organic compounds and odors present in ambient air. By pulling these interfering species out of the calibration sample, the sensor’s zero and response calibration become more accurate and repeatable.

The other options don’t address chemical interference in the air sample: metal shielding blocks electromagnetic noise around the electronics, not chemical species; silicone membranes may alter or selectively filter gas diffusion but aren’t standard scrubbing materials for VOCs during calibration; electrical grounding reduces electrical noise but doesn’t remove contaminants from the calibration air.