and surrounding rock it is often necessary to reinforce side walls and a top surface of the passage 10 to prevent loose rocks from falling thus screens may be attached to the walls and top surface to prevent such rock falls before installing the container 12 the desired location in the passage 10 may be cleaned and floors blown backed to solid surface and also it may be backwashed down to fill in any spaces between screens and the actual surface of the passage 10 foam gaskets may be blown completely around the circumference of the passage 10 as indicated at 32 in fig1 5 to the greatest extend possible the surfaces of the foam gaskets will be left reasonably smooth so as to enable an essentially continuous contact to be made to the container 12 thereby forming an adequate seal with the container 12 turning to fig2 the container 12 would be laid on the floor of the mine and a drainage and ventilation pipe 42 detailed below would be installed a ventilation pipe 34 is then connected between a ventilation supply duct 36 of a ventilation system and the tube connector sleeve 24 fig3 air is blown into the container 12 to inflate the container 12 and thus to expand the container until it fills the passage 10 contacting the gaskets 32 as indicated in fig4 and 5 it.