Oxygen concentrators extract 90-95% pure oxygen from ambient air using pressure swing adsorption (PSA) technology, filtering out nitrogen through zeolite molecular sieves for continuous therapy without cylinders or refills. Stationary home units deliver 1-10 LPM via nasal cannula to COPD, heart failure, or post-COVID patients requiring long-term oxygen. Compressor draws air through HEPA filters, pressurizes it into alternating sieve beds where nitrogen adsorbs, releasing oxygen to a reservoir. Electronic controls cycle beds for uninterrupted flow; digital displays show purity, flow rate, and alarms for low oxygen (<85%) or power failure.