It was, he said, "by far the lowest" ozone readings ever made on that date.

In the same spirit, Mr. Krupnick would average ozone readings over all monitors in an area rather than simply recording the worst case.

Pollution-monitoring equipment around the city has been showing high ozone readings for two weeks now.

Ground-level ozone readings had reached alarming levels, especially in Houston, and the testing program was developed by the state to meet federal clear-air requirements.

Certain examples of cities with elevated ozone readings are Houston, Texas, and Mexico City, Mexico.

During periods when ozone readings have been highest, peak concentrations in Page were noted to be more than 10 percent lower than those at the Grand Canyon.

The Steger team is said to have trained hard and realistically for its task, and plans to gather meteorological data, snow samples and ozone readings.

He said there had been as many days this year with ozone readings above the Federal standard as there were in all of 1986.

Along the route, team members will engage in some scientific experiments, recording meteorological data, gathering snow samples and taking ozone readings.

The next lowest level of ozone readings allows the agency to invoke the measures at its discretion.