Health & Medicine

When will this Spare the Air spell end? The latest from air quality officials

Friday is the 15th consecutive Spare the Air day for the Sacramento area, marking an unusually unhealthy summer for air quality. The streak, kept alive by intense wildfires burning across Northern California, is the longest in the region’s history, said Lori Kobza, spokesperson for Sacramento Metropolitan Air Quality Management District.

The previous record was 9 straight days in 2006, but Spare the Air standards have evolved since than, Kobza said.

Assuming fire conditions don’t worsen, that streak will end Saturday, Kobza said. Both ozone and particulate matter levels (PM2.5) are expected to be “dramatically improved” across the region as smoke partially clears on Saturday and Sunday, Kobza said.

That’s because of a low-pressure system predicted to blow from the southeast to the northwest, said Craig Shoemaker, spokesperson for the National Weather Service.

The wind pattern should visibly improve smoke and haze levels for those in the southern Sacramento Valley and northern San Joaquin Valley.

But cities north of Marysville, as well as foothill cities like Grass Valley and Placerville, won’t get as much of a respite, as the Mendocino Complex and Carr fires should continue to send smoke their way, Shoemaker said.

Shoemaker emphasized that the low-pressure system represents only a “temporary reprieve.” As long as fires are still burning, which they’re expected to into September, residents should always check their area’s current conditions on the Spare the Air website before engaging in prolonged outdoor activity or cracking open windows, Shoemaker said. Conditions can change hour to hour.


This live-updating map shows the combined readings for particulate matter and ozone.
AQI Animation -

Air quality levels reflect the concentration of small, harmful particles in the air.

Small particulate matter within wildfire smoke poses a direct threat to human health. Whereas a human hair is 60 micrometers in diameter, particles large than 10 micrometers can irritate a person’s eyes, nose and throat, according to information from the Office of Environmental Health Hazard Assessment.

Particles smaller than 2.5 micrometers can reach the lungs. These particles are so small, they can pass through the lungs and reach the bloodstream.

Along with PM2.5 upticks, heavy smoke usually worsens ozone production. Combustion produces nitrogen oxides that, in the presence of the sun’s ultraviolet rays, react with volatile organic compounds (VOCs) to produce ozone.

On Friday morning, every monitoring site for ground level ozone in the Sacramento region reported either orange (unhealthy for vulnerable groups) or red (unhealthy for everyone) ozone levels, as averaged over the previous 8 hours, Kobza said.

Occasionally, smoke will coagulate in a way that imitates cloud cover, preventing ultraviolet light from enabling the reaction, but that’s only occurred once in the recent fire season, according to Kobza.

Still, orange ozone levels (unhealthy for sensitive groups) are not unusual for the summer months, Kobza said. The molecule is an essential component of the Earth’s upper atmosphere, but it’s unhealthy and synonymous with smog when present in altitudes closer to sea level.

Meanwhile, residents hoping to be awestruck by the Perseid Meteor Shower, which is expected to be particularly visible on Saturday and Sunday night according to, might want to head out of the city, Shoemaker said.

Haze – smoke that’s been pushed above 1,000 feet – will likely partially obscure the shower, as will urban light pollution. Shoemaker recommended heading to the coast near San Francisco, or a longer road trip to Southern California, for those who want to fully appreciate the meteors.

The Bee’s Hannah Holzer contributed to this report.

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