Public-health scholars debate whether studies of wildfire smoke overstate its health effects because smoky days often coincide with heat, or understate them because people stay indoors and reduce exposure. A new analysis used indoor-sensor data and compared equally hot days with different smoke levels. It found increased respiratory symptoms even among people who stayed indoors, but the increase was smaller in buildings with effective filtration. The authors conclude that heat confounding does not explain the association, while avoidance behavior and building protection reduce measured average effects. Standard outdoor pollution readings, therefore, capture a genuine hazard but conceal large differences in actual exposure.