Humans breathe in oxygen, which is a vital gas for our survival. Upon inhalation, oxygen enters the lungs and diffuses into the bloodstream via the alveoli (tiny air sacs). Oxygen is essential for cellular respiration, a process that allows cells to produce energy by converting glucose into adenosine triphosphate (ATP) using oxygen. In addition to oxygen, humans also inhale nitrogen and trace gases, but oxygen is the primary gas required for the functioning of our bodily systems. Without adequate oxygen supply, vital organs can fail, leading to serious health issues.