The presence of closed porosity in fossil coals is shown. The technique of
definition of closed porosity is developed. Volumes of closed pores for coa
ls of the various sorts are determined experimentally. It is established th
at the contribution of closed pores in total porosity in most cases exceeds
60%. The tendency of closed pore volume to increase in outburst-prone coal
s is found out. (C) 1999 Elsevier Science Ltd. All rights reserved.