1.The portable phlegm suction unit is applicable to suck thick liquid such as pus—blood and phlegm under negative pressure. 2.Oil-free piston pump helps to keep from oil mist pollution. 3.Plastic panel makes it resistant from water erosion. 4.Overflow valve helps to prevent liquid from flowing into pump. 5.Negative pressure is adjustable according to requirements. 6.Small volume and light weight, easy to carry, especially suitable for emergency and doctors going their rounds outsides.