WHILE DRIVING A CAT TRUCK, EE STATED HE STARTED SMELLING COOLANT FROM THE HEATER CORE AT APPROX 12:00. HE WAS NAUSEOUS & VOMITED. HE REQUESTED A MECHANIC. WHEN MECHANIC ARRIVED, EE REPORTED TO HIS SUPERVISOT THAT HE WAS ILL. EMT ADMINISTERED OXYGEN THEN TRANSPORTED EE TO THE ER. ER DR OBSERVED & RELEASED. OXYGEN WAS GIVEN FOR 1 1/2 HOURS. AIR FRESHNER IN VENT CAUSED THE ODOR.