How did the Canadian wildfires show up in Home Assistant here in VA?

A few weeks ago, the Canadian wildfire haze reached Central Virginia, where I live, and we noticed it as a haziness in the air. Well, I have an AirGradient Open Air (model O-1PST) outdoor sensor and two AirGradient ONE units (model I-9PSL) indoor sensors. I'm a data-driven person, and I was instantly curious how this was showing up to the sensors in Home Assistant. Here's what it looked like in the sensor logs: Hourly mean PM2.5, 17-18 July 2026, central Virginia. The shaded band spans the two indoor sensors; the dashed line is the EPA 24-hour "unhealthy for sensitive groups" breakpoint (35.4 µg/m³). The signal was unmistakable. Outside, PM2.5 peaked at 164 µg/m³, against a normal range of 7 to 15 for that sensor. Inside, both sensors traced the same curve at about a quarter the height, topping out near 38. What I didn't expect was the timing. Outside peaked at 9 a.m., but inside didn't level off until noon. And the house was slower to clear than the air outside was. At the worst of…