Maricopa County is under an ozone High Pollution Advisory on Wednesday, Oct. 7, after state forecasters said ground-level ozone could exceed the federal health standard.
The county advisory, posted Wednesday, applies throughout the West Valley and the rest of Maricopa County. Residents are advised to limit outdoor activity while it is in effect, particularly children, older adults and people with asthma or other lung disease.
As of 2:30 p.m. Arizona time Wednesday, the advisory remained posted for Oct. 7. It is an ozone alert, not a dust or smoke advisory.
What the advisory restricts
Residential wood burning is prohibited during the advisory, including fireplaces, chimeneas, outdoor fire pits and similar fires. The restriction also applies to people and businesses with open-burning permits.
Government employees and contractors may not operate leaf blowers. The county encourages residents and businesses to avoid leaf blowing as well. Officials also advise avoiding off-road vehicle use.
The county recommends reducing vehicle trips when possible, avoiding long drive-through waits, refueling after dark or during cooler evening hours, and postponing painting or other solvent-heavy work until the advisory has passed.
Why ozone can build on a clear day
Ground-level ozone is not emitted directly. It forms when nitrogen oxides and volatile organic compounds from vehicles, fuel-powered equipment, industry and other sources react in sunlight. Hot, sunny and relatively stagnant conditions can allow concentrations to rise even when the sky looks clear.
The ADEQ Phoenix forecast page was last visibly updated Tuesday morning. It projected a Wednesday ozone Air Quality Index of 97, near the 101 threshold for the “Unhealthy for Sensitive Groups” category, with a maximum eight-hour average of 69 parts per billion. The county issued the High Pollution Advisory Wednesday based on an expectation that ozone would exceed the federal standard.
ADEQ’s Tuesday forecast called for ozone to ease later in the week as winds increase, clouds build and rain chances return. Because forecasts can change, residents planning strenuous outdoor activity should check the current county or state air-quality status before going out.
West Valley monitoring locations
Maricopa County operates air-monitoring sites across the region. Its published station list includes West Valley monitors at Buckeye Highway 85 and Maricopa County Highway 85; Dysart and Bell roads; 59th and Olive avenues in Glendale; and 109th Avenue and Deer Valley Road at Zuni Hills.
A monitor reports conditions at its location, so readings can vary across the county. The regional advisory remains the practical guide for Wednesday’s restrictions and health precautions.
Featured image: Original West Valley Post editorial illustration. It is not a photograph, official forecast map or monitor reading.
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