As the core equipment for oxygen therapy, oxygen concentrators extract oxygen from the air through physical or chemical technologies, and are widely used in medical first aid, chronic disease management, and daily health care. Starting from technical principles, classification and selection, application scenarios, and usage specifications, this article analyzes how this "life-empowering device" has become a guardian of family health. Data shows that the global demand for oxygen concentrators surged in 2021, with China's output increasing by 98.1% year-on-year, reflecting the social reality of an aging population, a high incidence of chronic diseases, and enhanced health awareness. This article aims to provide users with a scientific cognitive framework to help them understand the value and boundaries of oxygen concentrators, making every breath of oxygen a footnote to health.