Fig. 4. Non-steady-state diffusive flux estimator goodness-of-fit (²) to simulated headspace concentrations (closed symbols) and flux (f₀) estimation accuracy (open symbols) in response to an instantaneous pressure perturbation (P) induced at t = 0 min (positive perturbation) or at t = 10 min (negative perturbation). Data represent an experimental time constant = 610 min. The solid lines are not fits, but connect the data points to aid the eye.