An elderly Arlington woman has serious burns after she barely escaped a house fire early this morning.  The fire that began when she fell asleep while smoking -- while hooked up to a supplemental oxygen tank.  Arlington Fire Battalion Chief David Stapp says the woman was able to call 911 herself.  She and a tenant were in the home near the UT Arlington campus -- the tenant is okay but the woman is being treated at an Arlington hospital.  Firefighters say it could have been much worse -- because oxygen fires can be explosively hot and fast-moving.