This book examines the process of accumulation of gases in a known volume, initially at high vacuum, which is referred to as a constant volume (CV) technique. This technique allows for the measurement of very low gas flows, otherwise not detectable by any direct flow measuring device. The CV technique has been implemented into a time lag method used commonly for the determination of diffusivity, solubility and permeability coefficients in homogeneous films. Although not explicitly stated, the CV technique and the time method assume no resistance to gas transport within the volume...