AirNow's fire map includes data from PurpleAir sensors (that's what the little circles represent), and Watch Duty, a nonprofit fire tracking app, also displays PurpleAir data. But probably due to different calculations and processing delays, the air quality index reported by the same sensors can vary widely from map to map. For what's known as PM2.5 pollution, or small inhalable smoke and dust particles, a PurpleAir sensor south of Los Angeles International Airport on Monday simultaneously returned an air quality index of 28 on AirNow's website, 20 on WatchDuty and 5 on the PurpleAir website. official page.
Each of these values generally indicates healthy air, but things can become more complicated when other types of data are added to the calculations. That's exactly what companies like BreezoMeter and Ambee are doing in the hopes of providing what they describe as accurate “hyperlocal” estimates in the many miles between some sensor locations.
BreezoMeter was founded in Israel and raised tens of millions of dollars in venture capital funding before Google acquired it for more than $200 million in 2022, Israeli media said. (Google declined to comment on the deal value.) It's based on the air quality data seen in the Weather app on Apple devices and the Google Maps app. Indian startup Ambee, meanwhile, is responsible for the air quality data in the WeatherBug app, one of the most popular weather apps in the world.
Yael Maguire, vice president of geo-sustainability at Google, says BreezoMeter estimates air quality on an hourly basis for a wide range of pollutants and locations, generating more data than many government systems. To make its calculations, the company uses information coming not only from the EPA and PurpleAir sensors, but also from satellites and other sources such as weather and traffic reports. Similar data is included in Ambee's proprietary algorithm, according to Ambee CEO Jaideep Singh Bachher. “We want to give people the right data wherever and whenever they need it,” he says.
Volckens says he does not trust these systems. The cheap PurpleAir sensors they partially use are not well suited to the conditions they are often deployed in in the U.S., including during wildfires, he says. But he acknowledges that while these sensors are often off when it comes to the raw numbers, they can be accurate about 90 percent of the time in determining the advisory level — that scale from green to maroon that is often enough for people to to make decisions. on how to protect their health.
Andrew White, a representative for PurpleAir, says the sensors have proven to be accurate and that the company has no control over how other services perform calculations using their data. Google's Maguire says the company delivers “leading, highly accurate air quality information,” even in areas with limited monitoring.
Jennifer Richmond-Bryant, an associate professor of forestry and environmental resources at North Carolina State University who has studied PurpleAir sensors, says the safest bet for anyone concerned about air quality is to rely on the highest number or color level between different services . “I have more confidence in the AirNow numbers because I understand them,” she says. But “it never hurts to make an overly conservative decision when it comes to protecting yourself.”
