How can you increase the human oxygen level
im not exactly sure what you mean by that but do you mean like, increasing your lung capacity? if so then this is done by doing things like incrasing your physical activity breathing deeply and breathing exerscises running swimming and exerscising in water training in higher altitude and playing any wind instrument also total lung capacity depends on a persons age, height, sex, weight and degree of physical activity also smoking affects it hope that helped!