This story has been updated with additional resources.
It’s been a week since the deadly, massively destructive Camp Fire started in Northern California, and in a huge swath of the state, the smoke-filled air is still unsafe to breathe. If you live in San Francisco, or in Sacramento–where the air quality index reached 235 yesterday, well into the “very unhealthy” category–and you’re wondering how bad the pollution is in your neighborhood, an app called Blueair Friend will tell you in real time.
The company Blueair manufactures air purifiers; the Friend app connects with the company’s indoor monitor, which measures levels of particulate matter pollution inside an apartment or house. But it also shares detailed, global data about air quality based on outdoor sensors, and it’s free for anyone to use.
Unlike the EPA’s AirNow site, which only lists data from a handful of sensors (in San Francisco, for example, AirNow only publishes readings from a single location), the Blueair app is much more detailed. When I enter my own address in Oakland, it lists the pollution level from a location a couple of blocks away. The app’s map shows how the smoky haze varies by neighborhood; a few miles from me, the pollution has temporarily dropped from “unhealthy” to a “slightly unhealthy” category.
The app also shares pollution data in real time, whereas the government site is a couple of hours behind–and because air quality tends to quickly change, old data isn’t as useful. The app is powered by Breezometer, a company that uses algorithms and machine learning to analyze the government’s sensor data–combined with air dispersion models, weather data, traffic conditions, satellite data and more–to precisely estimate air quality to the resolution of a city block, in real time. You can compare the estimates with readings from PurpleAir, a grassroots network of sensors in backyards, or OpenMap, another community-based network of sensors.
The Blueair Friend app is available everywhere. When I last checked, New Delhi, one of the most polluted cities in the world, had air quality index of 165. My corner of Oakland had an AQI of 182. In Beijing, where the government is working to cut smog, the AQI was 40.