Air Quality in Pasadena, California — Live

Live readings from PurpleAir sensors across Pasadena — with free alerts the moment the air turns.

Live Pasadena AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Pasadena and Altadena, Sierra Madre, South Pasadena, San Marino, Arcadia, La Cañada Flintridge.

Pasadena sits at 863 feet at the foot of the San Gabriel Mountains, about 10 miles northeast of downtown Los Angeles, with the Angeles National Forest greenbelt above it, the Arroyo Seco cutting through it and the San Rafael Hills on its western side. Those mountains give the city about 20 inches of rain a year, roughly six more than Los Angeles gets, because air rising over the range drops its water here. The same wall that squeezes out the rain also pens in the air, and it is why Pasadena has been on the wrong end of two very different air problems — the photochemical smog that was first explained in a laboratory in this city, and, in January 2025, the smoke and ash of a fire that burned right at its northern edge.

Canairy watches the sensors around your home, your kids' school, and everywhere else you care about, and tells you in plain English when the air changes enough to matter.

The Eaton Fire and the weeks after it

The Eaton Fire started at about 6:18 p.m. on 7 January 2025 in Eaton Canyon, during a Santa Ana wind event that produced gusts of 100 mph at Mount Lukens in the eastern San Gabriels. It burned 14,021 acres before it was fully contained on 31 January, 24 days later. Nineteen people were killed. As of 21 January, 9,418 structures had been destroyed and a further 1,071 damaged, most of them in Altadena immediately north of the city, with portions of Pasadena itself also destroyed. In September 2025 the US Department of Justice sued Southern California Edison, attributing the fire to faulty power lines.

For anyone downwind, the numbers that mattered were the ones on an air monitor. Regional air quality index readings passed 200 into the Very Unhealthy category, and California Air Resources Board data recorded a one-hour peak of 483.7 micrograms per cubic metre of PM2.5 at the Los Angeles-North Main Street station. Because the fire consumed houses rather than only brush, the smoke carried what houses are made of: the CDC later reported a 110-fold increase in air lead levels during the fires, from the combustion of painted surfaces and pipes in pre-1978 structures. Los Angeles County Public Health extended its smoke advisory through 5 p.m. on Saturday 11 January, naming the area of Altadena and Pasadena, and Pasadena Unified School District closed through Friday 10 January.

What the testing found afterwards

The follow-up is worth knowing, because the honest version is more reassuring than the rumour version. Pasadena Public Health conducted environmental testing at nine city facilities, and South Coast AQMD ran mobile air monitoring across the area on 31 January 2025. No asbestos was detected at the city facilities. Lead measurements fell below the US EPA's Dust Lead Action Level of 5 micrograms per square foot. The mobile monitoring found no elevated levels of heavy metals such as lead or arsenic, or of benzene, with results remaining within background levels and below both national standards and state health thresholds. Elevated methane was detected in Altadena, possibly indicating gas leaks.

On the strength of that data the city amended rather than ended its local health emergency declaration, with acting health officer Parveen Kaur explaining that the department was updating it to reflect the priorities posed by current conditions — reducing contaminant exposure, safe removal of toxic substances from private property, and access to recovery funding. Pasadena Public Health's advisory of 17 January had already set out what to do indoors, and it is still a sensible template for any smoke event: wear a NIOSH-approved N95 or P100 respirator while cleaning your home, even if you were not directly affected; run a portable air cleaner with both a HEPA filter and an activated carbon filter, since the HEPA element removes 99.97 percent of the fine particles that reach deepest into the lungs; and fit MERV 11 or 12 filters in the furnace or HVAC, changing them monthly until the smell is gone.

The older problem, and why the mountains matter

Long before the fire, Pasadena had a claim on air quality history. Arie Haagen-Smit, a professor at Caltech here, began investigating air pollution in 1948 after Southern Californians started suffering stinging eyes and respiratory irritation and crops in the basin began showing damage. He showed that the haze was not simple soot but the product of a photochemical reaction, with sunlight acting on unburned hydrocarbons, ozone and nitrogen oxides from vehicle exhaust and industrial fuel combustion. By the mid-1950s the link between cars and Los Angeles smog was broadly accepted, and in 1968 Haagen-Smit was appointed the first chairman of the California Air Resources Board.

That chemistry has not gone away, and Pasadena's geography still favours it. Ozone is a hot-afternoon pollutant, not a cold-morning one, because it needs strong sunlight to form, and the San Gabriel Mountains at the city's back hold the air in place long enough for the reaction to run. It is the reason a day can look perfectly clear and still be a bad day to run the Rose Bowl loop or leave a school field session outdoors — and the reason a live number beats a look out of the window.

Pasadena air quality FAQ

Why is there smoke in Pasadena today?

Most often a wildfire in the San Gabriel Mountains or the Angeles National Forest directly above the city, or one further out in the basin whose smoke has drifted in and settled against the range. The clearest recent example was the Eaton Fire, which started on the evening of 7 January 2025 in Eaton Canyon, burned 14,021 acres before containment on 31 January, and put Altadena and Pasadena under a Los Angeles County smoke advisory that was extended through 5 p.m. on 11 January. Regional AQI readings passed 200 during that week. Smoke is not the only cause of a bad number here, though — ozone builds on hot, sunny afternoons with no fire involved at all.

What is the air quality in Pasadena right now?

This page shows the live AQI for Pasadena, calculated from PurpleAir sensors around the city and updated continuously. Pasadena runs from the flats near South Pasadena up to the base of the San Gabriels, and elevation and distance from the mountains both change what a sensor sees, so a reading at the north end of town and one near the 110 will not always agree. The sensors closest to your home and your children's school are the ones worth watching.

Is ash from the Eaton Fire still a health concern in Pasadena?

Pasadena Public Health warned on 17 January 2025 that ash can irritate skin, eyes, nose and throat, make breathing difficult and aggravate asthma, and advised everyone to wear an N95 or P100 mask when cleaning their home, whether or not they were directly hit by the fire. The testing that followed was largely reassuring: nine city facilities showed no asbestos and lead below the EPA's Dust Lead Action Level of 5 micrograms per square foot, and South Coast AQMD mobile air monitoring on 31 January found no elevated heavy metals or benzene, with results within background levels. The city amended its local health emergency rather than ending it, keeping the focus on safe removal of contaminants from private property.

Why does Pasadena have a reputation for smog?

Because the science of Los Angeles smog was worked out here. Arie Haagen-Smit at Caltech began his air pollution research in 1948 and demonstrated that the haze came from a photochemical reaction between unburned hydrocarbons, ozone and nitrogen oxides from car exhaust and industrial combustion, driven by sunlight; he went on to become the first chairman of the California Air Resources Board in 1968. The conditions that made Pasadena a good place to study the problem have not changed. Strong sun, a large basin full of traffic, and the San Gabriel Mountains standing directly behind the city to hold the air in place.

What AQI level is unhealthy?

Under the US EPA scale, AQI 0–50 is Good and 51–100 is Moderate. From 101 the air is Unhealthy for Sensitive Groups — kids, older adults, and people with asthma or heart conditions — and above 150 it's Unhealthy for everyone. Canairy translates these numbers into a plain-English verdict, like whether to close the windows or move a workout indoors.

Is Canairy free?

Yes. The Canairy app is free to download and includes live air quality for all your saved places, plain-English verdicts, and free push alerts when the air crosses your threshold. A paid plan adds extras like SMS text alerts.

Get Canairy free on Google Play.