Which environmental condition can influence VOC sorbent performance during sampling?

• A. Altitude
• B. Time of day
• C. Temperature and humidity
• D. Visual lighting

Answer: (C)

Temperature and humidity are the environmental conditions that most directly affect how well a VOC sorbent captures and retains compounds during sampling. The sorbent works by adsorbing VOC molecules onto its surface and into its pores, and this process is driven by temperature. When the ambient temperature rises, the molecules gain more energy and are more likely to desorb from the sorbent, increasing the chance of breakthrough and underestimating the true air concentration. Cooler conditions generally favor adsorption and retention.

Humidity introduces water molecules that can compete with VOCs for sorption sites, occupy pore spaces, or cause changes in the sorbent’s structure. This competition can reduce the sorption efficiency for many VOCs, alter breakthrough behavior, and complicate recovery during desorption, potentially leading to biased results. Some sorbents are more affected by moisture than others, so humidity monitoring and, if needed, moisture control or using humidity-tolerant sorbents are important for accurate sampling.

Altitude, time of day, and visual lighting don’t directly influence the sorbent’s capacity to capture VOCs in the same way, since they don’t alter the fundamental interaction between the sorbent and the target compounds during the sampling process.