As soon as breathing stops, the body begins using the oxygen already present in the lungs and bloodstream while carbon dioxide starts accumulating. It is the rising carbon dioxide levels, not falling oxygen alone, that usually create the powerful urge to breathe. Contrary to popular belief, the earliest trigger is not falling oxygen but rising carbon dioxide levels. As breath-holding continues, oxygen levels eventually begin to fall, which can impair concentration, judgment and coordination. “However, these benefits are generally seen in structured settings and should not be confused with attempting to hold one’s breath for as long as possible.”