Smog Alert Issued for Simi, Moorpark : Environment: Officials say the air is also expected to be unhealthful today. Temperatures in the 90s turn pollutants to ozone.

Patients at convalescent hospitals and children at nursery schools in the Simi Valley and Moorpark areas were advised to stay indoors until 6 p.m. Friday after air-quality officials declared that smog had reached unhealthful levels for certain people.

Officials at the Ventura County Air Pollution Control District also predicted that the air would be unhealthful from 1 to 4 p.m. today for people whose lungs are especially sensitive to smog.

Those considered particularly sensitive to air pollution include the elderly, the infirm, young children and otherwise healthy people engaging in vigorous exercise.

At the Phoenix Ranch School in Simi Valley, where 200 children ages 2 to 12 converge daily for preschool classes or summer camp, school owner Amy Brown said Friday’s active sports schedule had to be scrapped in favor of activities that are “cooling and calming.”

“It’s hard because kids like to run and jump,” Brown said. “We were going to have races and contests because today is Pirate Day, but instead we are doing water play and playing in wet sand.”

The advisories for Friday and today--the second and third such warnings of the summer for the two cities--were called as temperatures soared into the 90s in eastern Ventura County, reaching 94 degrees in Simi Valley. The first health advisory was called Aug. 10.

Temperatures were expected to cool slightly in the eastern county today, but probably will remain in the low 90s, said Kent Field, Air Pollution Control District meteorologist.

“Welcome to summer,” Field said, noting the arrival of hot weather after three months of cool temperatures and foggy skies. He said some low clouds and slightly cooler weather probably will return early next week.

The hot weather provides the heat necessary to cook pollutants from cars and factories into ozone, an invisible gas that harms lungs and interferes with respiratory functions.

Under a new state law that took effect in January, the health warnings are issued when ozone levels reach 138 on the Pollutant Standard Index, the equivalent of 0.15 p.p.m. of ozone in the air.

Previously, no warnings were issued until ozone levels reached 200 on the index. The level at which warnings are issued was lowered because health officials determined that ozone causes lung damage at lower concentrations than was once believed.

The law requires that hospitals, schools and the media be notified when advisories are issued.

Ursula Christie, owner of the Tiny Tots Nursery School in Simi Valley, said her 40 preschool-age children stayed indoors Friday because of the smog advisory and the heat.

“We’re doing clay experiences and Play-Doh, the kind of thing that keeps the children quiet and happy,” she said.

At Hallmark Nursing Center of Simi Valley, Nursing Director Diane Lupi said patients who had been sitting outdoors at the 99-bed hospital and convalescent home willingly came inside when nurses told them of the health advisory.

“We told them they were better off sitting inside an air-conditioned room,” she said. “It’s been so warm here that we had great compliance.”

In Moorpark, Philip Newhouse, director of community services, said city maintenance workers had been directed not to exert themselves outdoors. They were told to limit themselves to inspections or other lighter-duty tasks.

Newhouse said the city’s municipal softball games are scheduled in the evenings and would not be affected by the smog warnings.

Ozone pollution diminishes in the evening as the emissions from cars and factories dissipate and the air cools. In addition, the high-pressure weather system that traps pollutants near the ground during the day weakens in the evening and allows them to disperse, Field said.

“We left the advisory on until 6 p.m. Friday just to be sure we catch all the highest concentrations,” he said. “But even after 6, the ozone level will still be higher than the federal health standards.”