What is used to limit interference with fresh air calibration with the MultiRAE Pro?

• A. Ion exchange resin
• B. Polymer membranes
• C. Charcoal Filters
• D. No filter is required

Answer: (C)

When calibrating the MultiRAE Pro with fresh air, the goal is to set a true zero using clean, uncontaminated air. Ambient air often contains VOCs and other organic compounds that can bias the sensor baselines, especially for electrochemical and PID readings. Activated charcoal filters scrub these organic vapors from the calibration air, reducing interference so the zero reference reflects truly clean air. This makes the calibration more accurate and repeatable.

Ion exchange resin is designed for ion removal in liquids, not air calibration. Polymer membranes could alter gas throughput and aren’t the standard method for scrubbing VOCs during fresh-air calibration. Skipping any filter would allow ambient contaminants to skew the zero. Therefore, charcoal filters are the appropriate choice because they effectively remove interfering VOCs from the calibration air.