New device from a private hospital I bought it. Oxygen flow: from 0.5 to 5 liters/minute. * Oxygen concentration: approximately between 87% and 95.5%. * Noise level: less than 55 decibels (relatively quiet). * Works continuously for 24 hours. * LCD display screen. * Equipped with wheels for movement and mobility. * Contains alarm system for malfunctions and power outages. * Oil-Free Compressor. With nebulizer/inhaler function. Its price is 2500 and negotiable.