Learning Data Science

Chapter 12. Case Study: How Accurate Are Air Quality Measurements?

California is prone to wildfires, so much so that its residents (like the authors of this book) sometimes say that California is “always on fire.” In 2020, 40 separate fires covered the state in smoke, forced thousands of people to evacuate, and caused more than $12 billion in damages (Figure 12-1).

Figure 12-1. Satellite image from August 2020 showing smoke covering California (image from Wikipedia licensed under CC BY-SA 3.0 IGO)

In places like California, people use air quality measurements to learn what kinds of protective measures they need to take. Depending on conditions, people may wish to wear a mask, use air filters, or avoid going outside altogether.

In the US, one important source of air quality information is the Air Quality System (AQS), run by the US government. AQS places high-quality sensors at locations across the US and makes their data available to the public. These sensors are carefully calibrated to strict standards—in fact, the AQS sensors are generally seen as the gold standard for accuracy. However, they have a few downsides. The sensors are expensive: typically between $15,000 and $40,000 each. This means that there are fewer sensors, and they are farther apart. Someone living far away from a sensor might not be able to access AQS data for their personal use. Also, AQS sensors do not provide ...