of the mine 's two airtight rescue chambers . `` The rescue teams have taken four breathing apparatuses with them , '' Stricklin said . `` In the best case scenario , we would find four survivors . Once they get in there , we 'll put oxygen masks on the survivors and bring them out . '' At least 25 miners died in Monday afternoon 's explosion in West Virginia , while four others remain missing and two were injured . Rescuers -- 32 of them working in four teams -- got within 500 feet of one of the rescue chambers before having to turn back Thursday , said J. Christopher Adkins , chief operating officer of Massey Energy , the mine 's owner . They were pulled back after it was determined that noxious gas levels were high enough to cause another blast . The readings showed potentially explosive levels of methane and hydrogen and high levels of carbon monoxide . Stricklin said air samples were tested at regular intervals Thursday night and that rising barometric pressure in the wake of a cold front that moved through the region had helped reduce the chances of another blast .
Naoma , West Virginia -LRB- CNN -RRB- -- Crews planned to pump nitrogen into a West Virginia coal mine as the search resumed early Friday for four miners who may be trapped after a deadly explosion earlier in the week . Kevin Stricklin of the U.S. Mine Safety and Health Administration -LRB- MSHA -RRB- said crews would neutralize potentially explosive air in the Upper Big Branch coal mine with nitrogen , allowing rescuers to go back in and remain there even if an explosive mixture builds again in the air . The hope , though slim , is that the four missing miners were able to survive by entering one of the chambers , which were stocked with enough food , water and air to keep 15 miners alive for four days . `` We committed to the families that we wanted to get into the chambers within 96 hours and we 're trying to everything in our power to do that without taking a chance on the rescue teams , and I think this is the way to do it , '' Stricklin said . Officials said the rescue teams will make `` a mad dash '' to one