Have you ever wondered how the air in a small cave that receives thousands of visitors is renewed? This is a question that we tried to answer in a talk held on February 25th 2026 at Faculty of Sciences at USAL.

In most cases, air renewal within a cave occurs naturally through the ventilation of the karst system. Many caves have airflow patterns that change direction, similar to breathing. However, while we inhale and exhale every few seconds, in most caves the change in ventilation pattern is seasonal. Although there are various mechanisms for natural cave ventilation, the most common cause is the temperature difference between the outside and inside of the cave, which affects the density of the air masses. Understanding the mechanisms by which air moves in caves is important because it influences the concentration of CO2 in the cavity, which in turn affects the hydrochemistry of the dripping water and, consequently, the precipitation (or dissolution) of speleothems. Therefore, cave ventilation significantly affects the growth of formations throughout the seasons. Furthermore, very high CO2 levels can be harmful to health, so understanding the natural dynamics and differentiating them from the effects of visitors is important in tourist caves. In this talk, we examined the ventilation of the Cueva del Águila (Ávila) using air density calculations. The conceptual model presentied has been independently compared with a carbon isotope study, which also allowed us to determine the origin of the cave’s CO2.