Modern concepts of changes in the oxygen content in the Earth's atmosphere

Oxygen is vital for humans and animals. Nevertheless, undeservedly inadequate attention has been paid to trends and variability of its content in surface air until recently. This is due to the fact that the percentage of oxygen in the Earth's atmosphere varies slightly, and the fact that measuring these small changes is a rather difficult technical task. However, even small changes in the oxygen content in the inhaled air turn out to be very sensitive for people, especially during heat waves, which are becoming more frequent and intensified in conditions of rapid climate change. This review is devoted to the history of the development of knowledges about changes in oxygen content in the atmosphere and a review of research in recent decades, when the results of measurements of oxygen content in background and urban conditions appeared.