Driving force for moisture transfer can be conceptually increased by maintaining head space at very high or very low vapour pressures. Under sub atmospheric pressures the sorption resistance due to interstitial air is low. Using this concept, the adsorption and desorption properties for polished rice have been measured under reduced pressure for theoretical interpretation of the process which can be used in commercial moisture adjusters to get even sorption of batch and to get rid of costly agitation. Data were collected for thick and one seed layers under different pressure conditions. In the thick layer trial, higher uniformity of sorption was found at lower total pressure conditions. One seed layer sorption trial was conducted for the determination of sorption coefficient "k" of the first falling rate moisture transfer equation for different temperature conditions. Predicted values of moisture were found to be in good agreement with observed data. Grain damage due to low pressure was investigated for different initial moisture polished rice, under 3, 40, 130, 200 and 380mm Hg pressure. Higher moisture polished rice was more liable to crack under reduced pressure. In the same trial the effect of head space humidity on seed damage was investigated introducing steam under pressure of 1.5kg
cm^2 into the equilibration chamber. According to the results cracks were all middle cracks and also high in low initial moisture polished rice.