When an alarm designed to signal a leak of a dangerous gas went off twice in one day at a Woodland Hills hospital, it forced the evacuation of about 75 patients and employees, sent about 40 people to the emergency room complaining of minor symptoms, and required the attention of 15 fire companies and two hazardous-materials units.
Nevertheless, two weeks after the July 16 incident at the Kaiser Permanente Medical Center on De Soto Avenue, county health officials say the alarm was probably false.
"I know of no actual evidence that there was a leak," said Bud Pate, supervisor of the hospital-inspection unit of the county Department of Health Services.
The hospital alarm is designed to detect a gas called ethylene oxide, which is used to sterilize surgical equipment that is too heat-sensitive to be sterilized with steam. Low levels of the gas have been shown to cause cancer in animals and can cause nausea, headaches and irritation of the eyes and sinuses.
But Pate and other county health officials said that tests for the gas--conducted the day of the alarm and several times since then--found no traces of it.
'Exposed to Something'
The finding does not mean, however, that state and county authorities have concluded that the stricken people were merely victims of mass hysteria. "The employees were exposed to something," said Jim Mason, who has been following the situation at the hospital for CAL-OSHA, the state agency that monitors occupational safety and health.
Inspections and tests of a sterilization chamber that might have been the source of ethylene oxide disclosed no leaks or other problems, said Jose Ochoa, senior industrial hygienist with the health department's program to control hazardous waste.
Tests also detected no Freon, which is used to dilute the ethylene oxide in the sterilization chamber, Ochoa said. "When you test for Freon, if Freon is non-existent, then chances are--with great probability--that ethylene oxide is going to be non-existent as well," he said.
The attention of investigators has focused on the alarm system, in the basement near the sterilization chamber, Ochoa said. The wall-mounted sensors can be triggered by many substances, he said.
There is a supply of alcohol near the sterilizing chamber, Ochoa said, adding, "When alcohol vapors come close to the alarm, they set it off."
County health officials expect to receive a report from Kaiser Permanente within a few days summarizing the findings of the hospital's internal investigations of the incident, Pate said. The sterilizing equipment will not be reactivated until the report is evaluated, he said.
The hospital has been sending surgical supplies to a Kaiser Permanente hospital in Panorama City for ethylene oxide sterilization, a hospital spokeswoman said.