Sorption studies involving the sorption of n-propanol by an Amorphous Nylon(Nylon 6I/6T) were carried out as a function of sorbate vapor activity at $23^{circ}C$. Vapor activity levels from 0.035 to 0.91 were investigated to evaluate the concentration dependency of sorption mechanism. Sorption behavior of propanol by Nylon 6I/6T showed distinctive two mode sorption phenomena as a function of Vapor activity. At Vapor activity levels below a=0.11, equilibrium sorption was achieved within a short period of time(less than 20hrs), which can be interpreted as following a Fickian diffusion model. A Langmuir-Flory-Muggins Dual Mode Sorption model can also be applied at these concentration levels. However, for Vapor activities above a=0.11, the sorption process appeared to be non-Fickian and resulted in a lack of equilibrium being attained.