What is the purpose of using a backup sorbent in sorbent sampling?

• A. To calibrate the sampler
• B. To slow down sampling
• C. To reduce costs
• D. To prevent breakthrough by capturing contaminants that pass primary sorbent

Answer: (D)

Backup sorbent is placed downstream of the primary sorbent to catch anything that slips past the first sorbent during sampling. The primary sorbent traps most of the contaminants, but depending on factors like concentration, flow rate, and the chemical’s properties, some molecules can break through. If nothing downstream were there, those breakthrough contaminants would go undetected, leading to an underestimate of exposure. The backup sorbent captures these passing contaminants, helping ensure the sample reflects the total air concentration or at least signals that breakthrough has occurred. This is not for calibration, not to slow sampling, and not to reduce costs.