ST. LOUIS -- One more weekend of clean air and St. Louis could survive the summer without violating federal clean air standards.

Air-quality specialists were confident Monday that southwesterly breezes and ozone-conscious consumers helped ease the St. Louis area through the Labor Day weekend without violations.

Rick Taylor of the Missouri Department of Natural Resources said ozone levels peaked nearly halfway below the federal standard Monday and were falling by about 3 p.m. That made it unlikely that evening travelers returning home from the long holiday weekend would push the levels back up.

"We're going to make it," Taylor said after receiving word that the levels were on the way down.

The Labor Day weekend is a critical time for ozone levels because hot, stagnant weather and heavy holiday traffic can combine to create higher readings.

The high temperature Monday was 94. But Susannah Fuchs of the American Lung Association of Eastern Missouri said reduced emissions and steady breezes of 8 to 14 miles per hour helped to clear the air.

If the region can make it through the upcoming weekend, Fuchs said, it will be able to survive the summer without a serious violation.

Doing so would allow state officials to ask the U.S. Environmental Protection Agency to declare the region in compliance with clean air rules. A violation would open the door for a federal appeals court in Chicago to order costly pollution controls for area businesses, a remedy sought by environmental groups who filed suit over the issue.

Levels of ozone watched

Sixteen monitoring stations around the St. Louis area regularly take air samples and test them for ozone levels.

Ozone levels at one of the region's trouble spots peaked Monday at 0.065 parts per million, roughly half of the federal limit of 0.125 parts per million.

The station had recorded three violations in the past three years -- the maximum allowed by the U.S. agency.

Missouri Gov. Bob Holden had urged area residents to help hold down ozone levels over the weekend by limiting their daytime driving and turning off their air-conditioning systems.

Chris Byrnes, director of St. Louis County's air-pollution control program and chairman of the Regional Clean Air Partnership, said, "There's been a fairly concentrated effort in the metropolitan area to cut back over the weekend. We're at that kind of critical juncture here, and I think everybody understands what the issues are."