(Spokane, WA)  --  Officials at Fairchild Air Force Base near Spokane are trying to determine the nature of an unknown irritant that sent more than a dozen people to the hospital.  KREM-TV reports at least 28 people at the base's Logistics Readiness Station reported feeling affected yesterday by the mysterious irritant.  Fourteen of them were taken to the hospital, but were later released.  Fairchild officials say the problem appears to be contained in the Logistics Readiness Station ventilation system.