Peak ground ozone levels in parts per billion for last week:
• July 17 — 45.6 ppb
• July 18 — 41.6 ppb
• July 19 — 42.7 ppb
• July 20 — 35.5 ppb
• July 21 — 41 ppb
— Air quality alerts are generally issued after ground-level ozone exceeds 59 parts per billion.
Much of the U.S. has been sweltering under “the dome” — a stalled air mass that has caused record-setting temperatures — for the past week.
Along with those high temperatures, many Midwestern and eastern cities have experienced high amounts of ground-level ozone, a byproduct of hydrocarbons such as gasoline and oil.
In high amounts — anything greater than 59 parts per billion — ozone can cause breathing difficulties and lung injuries.
In Craig, however, ozone has not been an issue.
Roger Spears, a former Moffat County High School science teacher, said local ozone has been within tolerable limits.
“What I’ve seen has been lower than 55,” he said. “There hasn’t been any concern for an alert of any sort.”
Spears would know.
In May, Spears announced that the MCHS science department had joined the Global Ozone Project, a Denver-based nonprofit that compiles ozone data via a network of monitors that have been installed in classrooms throughout the world.
In exchange for its participation, MCHS received a laptop and ozone monitoring equipment, which has since been installed at Craig Middle School due to its more favorable roof.
Ground-level ozone is generally at its worst during summer months, particularly in July, Spears said.
“I would say so, because of the length of the day, the height of the sun and the higher temperatures, of course,” he said. “With the heat, and how hot it’s been nationwide, of course ozone levels are going to go up.”
Nonetheless, Craig air has performed well, according to sensor data found on the Global Ozone Project’s website, www.go3project.com.
Last week, on July 17, the highest level in Craig was recorded at 45.6 ppb.
Spears said ozone levels rise and fall in predictable patterns.
“There’s a very consistent curve where (ozone levels) drop off at night, then build up during the day,” he said. “It peaks at about 3 p.m. After that, once the sun starts going farther to the west, it starts reducing again.”
In June and early July, however, Spears said he noticed two periods of irregular ozone readings. One period of high levels coincided with regional wildfires.
“We had fairly high levels when we had smoke from the forest fire in Arizona in early June,” he said. “We had some spikes there, but that seemed to clear out when the wind changed direction.”
Another period coincided with recent construction at CMS.
“That was really the only abnormal thing we saw,” Spears said of the construction.
As of Sunday afternoon, the Global Ozone Project’s website did not contain data for Friday, Saturday or Sunday.
However, Norm Yoast, a science teacher at CMS, was able to check data from his home computer.
“Everything looks normal,” he said.
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