With an ingenious pressure relief valve and down spout diffuser, Salter's Tan Lid 7900 Bubble Humidifier Bottle provides effective, comfortable humidification for oxygen users with high flows of 6-15 LPM. As with all Salter Bubble Humidifiers, the 7900 Bubble Humidifier Bottle is safe and easy to use, maximizing humidification while ensuring quiet operation and lowering system back pressure.