The controlling effect of temperature in the application of permeation tube devices in standard gas generation.

In this study, the performance of permeation tube (PT) devices for the generation of VOC calibration gas was examined by successively generating BTX gas at five temperatures (30, 50, 70, 80, and 100 °C) and two flow rates (400 and 800 mL min⁻¹). A distinct relationship was observed between temperatures and permeation rates (PR) (or generated BTX concentrations). We examined the reliability of the manufacturer's PR formula when operating at chamber temperatures different from the manufacturer reference temperatures for each PT device. Bias of the actual PR from the theoretical PR values became significant as PT devices were operated at temperatures beyond their optimum operating range (e.g., maximum bias of BTX as 141%, 87.2%, and 85%, respectively). Through a derivation of empirical formula, we were able to predict PR values of the target compounds more accurately as evidenced by significant bias reduction at all temperature points (e.g., maximum bias of BTX as 10.9%, 21.1% and 20.6%, respectively).