Abstract: AN EXPLOSION IN THE BOILER ROOM AT THIS PLANT ON JANUARY 29, 1986 HAD RESULTED IN A TOTAL PLANT SHUT-DOWN. KEROSENE SPACE HEATERS WERE BROUGHT INTO THE PLANT TO KEEP THE PIPES FROM FREEZING WHILE REPAIRS WERE UNDERWAY. THE PLANT RESUMED OPERATION ON FEBRUARY THIRD. AFTER ABOUT AN HOUR AND A HALF OF OPERATION, EMPLOYEES BEGAN TO BECOME ILL. SEVEN EMPLOYEES WERE HOSPITALIZED. OF THE SEVEN, FIVE WERE FOUND TO HAVE HIGH CARBOXYHEMOGLOBIN LEVELS. MOSH ARRIVED AT ABOUT 2 PM, BUT BY THEN THE PLANT HAD BEEN AIRED OUT AND NO SIGNIFICANT LEVELS OF CARBON MONOXIDE WERE FOUND. BECAUSE OF THE HIGH LEVELS OF CARBOXYHEMOGLOBIN FOUND IN THE FIVE EMPLOYEES, IT IS SURMISED THAT THEY HAD BEEN EXPOSED TO A HIGH CONCENTRATION OF CARBON MONOXIDE. IT IS NOT KNOWN WHETHER THE CARBON MONOXIDE WAS GENERATED BY THE SPACE HEATERS, BADLY TUNED FORKLIFTS OR THE TEMPORARY BOILER. THE AFFECTED EMPLOYEES CAME FROM WIDELY SEPARATED AREAS OF THE PLANT.