The core principle of portable oxygen concentrators is based on molecular sieve adsorption technology (PSA), which physically separates nitrogen and oxygen from ambient air to achieve a continuous output of high‑concentration oxygen. Ambient air is pressurized by a compressor and then directed into adsorption towers filled with molecular sieve. Since nitrogen molecules (approximately 0.36 nm in diameter) are more readily adsorbed by the molecular sieve than oxygen molecules (approximately 0.28 nm in diameter), oxygen passes through and is collected.