Although it is displayed as the usage time limit (h) 23, 18 hours is printed on the mask. Because the valve is thin, the exhaust resistance is felt higher than 8822E-DS2. As the mask softens with humidity, the mask itself repeatedly shrinks greatly. Along with that, water droplets of Keba get stuck in their noses and mouths and it is unpleasant. There is no air leak around the nose. It seems that it can be used relatively comfortably for about 6 hours.