Abstract: A hypoxic room system for hypoxic training or therapy is provided which simulates oxygen-depleted mountain air. The system employs an oxygen content-reducing device (hypoxicator) which supplies oxygen-depleted air to a hypoxic training room communicating with the device and having ventilating openings for equalizing atmospheric pressure inside the hypoxic room. The system may be applied to interior space inside any structure. The hypoxicator may employ a membrane air-separation principle or a molecular sieve pressure-swing adsorption process.