For 24 hours starting at 8 a.m. Wednesday, Camarillo's Freedom Park will become home to a tent hospital and other emergency medical facilities as part of a first-of-its-kind training exercise for healthcare and other emergency workers.

The Ventura County Public Health Department is hosting the exercise, dubbed "Operation Sunset," to give public health, hospital and other emergency responders a sense of what they might face if hospitals reach capacity or are rendered useless by a large-scale disaster such as an earthquake or pandemic flu.

It is believed to be the first 24-hour training event for healthcare workers in Ventura County and possibly the state. About 250 people are expected to participate, including many public health employees, hospital staffers and ambulance crews, as well as other emergency workers and volunteer groups that assist in disasters.

Because of its unusual length and scope, the exercise also is drawing participants from many Southern California counties as well as the state Department of Public Health. The event is not open to the public.

"Never has a public health department had a 24-hour drill with shift changes," said Dan Wall, training and education coordinator for the county Public Health Department's Emergency Preparedness Office. "We never do drills for more than three or four hours."

But Hurricane Katrina's devastation showed public health officials that in reality, disasters could stretch on much longer, and workers need to be prepared for that, Wall said.

The exercise will help public health officials determine what pieces in their response chain might be missing or need correcting.

Operation Sunset will include classes and training exercises on mass care and shelter, finding and setting up alternate care sites, generator care, use of personal protective equipment, how to conduct mass prophylaxis clinics, even instruction on landing helicopters. The exercise will conclude at 8 a.m. Thursday.

Vendors are donating food, equipment and other materials for the event. American Red Cross volunteers will use the agency's new mobile kitchen to serve three meals at the site.

Many of the courses were developed to address problems that arose from Hurricane Katrina and its aftermath, or to learn how to use equipment or gear purchased with Homeland Security grants in the wake of Sept. 11. Millions of dollars have been spent to outfit local emergency agencies with supplies to use in the event of a terrorist attack or large-scale disaster, but the grants included little or no money for training in the equipment's use.

Wednesday's exercise will mean that "when a disaster or a medical disaster hits, we'll actually know how to use the equipment we have," said Linda Henderson, director of Ventura County Public Health.

"When your stress level goes up, your IQ drops, so you want to practice, practice, practice. You really want everybody to understand their role."