Oxygen concentrators

specifications 1. flow range: 1～5l/min   2. oxygen concentration: 95.5%～87% 3. maximum outlet pressure: 20kpa～50kpa (2.9psi～7.25psi)  4. pressure relief mechanism operational at:      250kpa±25kpa (36.25psi±3.63psi) 5. sound level: ≤55db (a) 6. power supply:     ac120v±10%   ac220v±10%   ac230v±10%     50hz  □60hz   7. input power: ≤400va 8. weight: 24kg (53 lbs) 9. dimension: h55.6cm (21.9″)×w28.5cm (11.23″)×d47cm(18.52″) 10. minimum operating time: 30minutes