A good oxygen concentrator, generally with oxygen concentration monitoring, do not worry about the concentration of oxygen will decline when inhaling oxygen, can be a long time or even 24 hours of continuous power. The two oxygen concentrators are both good. Zhongjin has one more promise than Invacare that it will replace the oxygen concentrator with a new one if there is a quality problem in 1500 hours, but Invacare has no similar promise. In the East Ring Road above, the Honghui Hospital on the north side of a specialized sell this, you can go to see, we are there to buy, where the price is the same as the evening