previously shown in fig2 the location of combustion face 14 is initially determined and a plan to fight the fire is formed a subterranean volume containing the fire is defined this volume will generally be less than the entire mine so the defined volume must be segregated from the whole in the example of fig5 stop wall 54 has been placed in drift 32 one way to place such a stop wall is to form and pour concrete with an included portal the portal includes a pressure tight hatch that can be closed and sealed at the appropriate time next every ventilation access port to the subterranean volume should be found a u201c ventilation access port u201d is any route whereby the subterranean volume is connected to the surface for example ventilation shaft 28 and natural vent 30 are both ventilation access ports it will often be desirable to add additional ventilation access ports in the example shown three bore holes 66 are added two of these are immediately adjacent to the combustion face the term u201c immediately adjacent to u201d means that these holes are close enough to the combustion face so that liquid carbon dioxide injected through these bore holes will promptly be converted to gas by the heat of the combustion face it is preferable that liquid carbon dioxide injected through these bore holes actually impinge upon a portion of the combustion face a flow control device is placed in each of the ventilation access ports the term u201c flow control device u201d means anything that alters the flow through a portal and may in fact simply mean plugging the portal the term also includes injection heads for injecting.