The fire department evacuated a building at the Redbird Trails apartments in southwest Dallas around 8:30 p.m. Tuesday.
One of the victims told FOX 4 that she had a headache and then began to vomit.
She blacked out and woke up at the hospital.
Her 16-year-old son is also being treated at Baylor University Medical Center.
Dallas Fire-Rescue officials said the source of the leak was a boiler room attached to the building.