Abstract: AT ABOUT 9 AM ON FEBRUARY 12, 1987, SEVERAL EMPLOYEES BEGAN TO COMPLAIN OF HEADACHES, LIGHTHEADEDNESS AND NAUSEA. THIRTY EMPLOYEES WERE SENT TO THE LOCAL HOSPITAL AND SEVEN OF THE THIRTY ADMITTED OVERNIGHT. BLOOD TESTS TAKEN BY THE TREATING PHYSICIANS DID NOT SHOW ANY ELEVATED CARBOXYHEMOGLOBIN LEVELS. OXYGEN HAD BEEN ADMINISTERED PRIOR TO THE COLLECTION OF THE BLOOD SAMPLES. TWO WEEKS EARLIER A NATURAL GAS LEAK HAD OCCURRED AT THIS SITE. SEVERAL PERSONS BECAME ILL AND THREE WERE HOSPITALIZED FOR OBSERVATION. NO NATURAL GAS LEAK WAS FOUND BY THE GAS COMPANY REPRESENTATIVE, WHO CAME TO THE SITE THE NEXT DAY. CARBON MONOXIDE WAS FOUND TO BE ESCAPING FROM OVERHEAD GAS HEATERS, BUT WORKPLACE AIR MONITORING SHOWED ONLY SLIGHTLY ELEVATED LEVELS. THE WORKPLACE HAD BEEN WELL VENTILATED BY THE TIME THE READINGS WERE TAKEN. THE GAS HEATERS WERE OLD, AND WERE REPLACED WITH NEW UNITS ON ON FEBRUARY 14TH. THE EMPLOYEES RETURNED TO WORK ON FEBRUARY 17TH. NO FURTHER PROBLEMS WERE REPORTED.