Anderson County Sheriff's Sgt. Steve Reeves says Elizabeth Whitfield was placed on a respirator late Tuesday at Greenville Memorial Hospital.
Authorities were called to Whitfield's home Sunday after she reported her youngest son was having breathing troubles. Jacob Whitfield died at a hospital, and 2-year-old Kenneth Whitfield has also been hospitalized.
Authorities say Elizabeth Whitfield had been using foggers to treat an insect problem and was coated in chemicals. She was released Sunday but was readmitted on Monday.
Toxicology results on Jacob Whitfield will take several weeks to complete.