AP Environmental Science (APES) Atmospheric Pollution Practice Test 2026 - Free APES Atmospheric Pollution Practice Questions and Study Guide

In cold weather, heating the inside of a building creates a stack effect: warm indoor air rises and leaks out of the upper parts of the house, while cooler air is drawn in at the bottom. This movement lowers the air pressure at the foundation, pulling soil gas from beneath the house into the living space through cracks and openings. That soil gas carries radon, so indoor radon levels rise when the indoor–outdoor temperature difference drives this suction.

Radon production in the soil itself doesn’t suddenly increase in winter, and radon is a gas that won’t condense with cold air. Higher indoor ventilation would actually dilute radon rather than raise it.