An investigation on the Consolidation by Atmospheric Pressure (CAPing) of a gas atomized commercial T15 tool steel powder is presented. The study was carried out over a range of temperature between 1150 and 1250 degrees C using loose powder encapsulated in Pyrex glass bottles. The densification mechanisms during CAPing process are subjected to several factors, such as sintering temperature and time, powder particle size and vacuum level. The results indicated that the densification of this powder can be enhanced by decreasing powder particle size and increasing the vacuum level, temperature and time of sintering. Glass penetration is a special characteristic of this process. At some conditions, the highly fluid glass may penetrate deeply throughout the powder aggregate and prevents it from densifying. This study has showed that during CAPing of T15 tool steel powder, there is a competition between the densification and the glass penetration rates. At high temperature (1250 degrees C) and high vacuum level (10(-5) tor), the pore closure rate is higher than glass penetration rate and this leads to full density of the material within only 1.5 h. However, at lower temperatures and vacuum conditions, the powder material needs much longer time to reach higher densities. Finally, it can be said that this process offers the possibility of closing the residual porosity and a good control of structural refinement, as well as a substantial production cost savings which could prove a crucial decision making parameter for industrial exploitation of the process. (C) 2019 Elsevier B.V. All rights reserved.