What is the approximate oxygen percentage in the normal atmosphere?

The approximate oxygen percentage in the normal atmosphere is around 21%. This figure is significant because it reflects the balance of gases necessary for respiration in humans and most animals, as well as for combustion processes. The atmosphere is primarily composed of nitrogen (about 78%) and contains a small percentage of other gases, including argon and carbon dioxide. Understanding the composition of the atmosphere is crucial in various fields, including safety and health, as deviations from this normal range can indicate potential dangers, such as oxygen deficiency in confined spaces or environments with poor ventilation.