从含油量上看，空压机中的有油与无油一般都是指空压机排气口排出气体的含油量的多少，一般有油机含油量较大，无油机的含油量为0.01ppm，所以用这个含油量来区分空压机有油与无油。还有一种是全无油的空压机，它不是采用有油润滑，而是采用树脂材料润滑，所以最终排出的气体不含油称为全无油空压机。
From the oil content point of view, the oil and no oil in the air compressor generally refers to the oil content of the gas discharged from the air compressor exhaust port. Generally, the oil content of the oil compressor is larger, and the oil content of the no oil compressor is 0.01ppm, so this oil content is used to distinguish the oil and no oil in the air compressor. There is also a completely oil-free air compressor, which is not lubricated with oil, but with resin material lubrication, so the final exhaust gas does not contain oil, so it is called totally oil-free air compressor.
从结构上看，无油空压机与有油空压机两者的轴承是没有什么区别的。但是从工作原理上看，二者就有明显的不同之处。无油空压机在运行的过程中是没有油的参与的，无论是无油活塞机还是无油螺杆机，它们在运行的过程中会产生大量的高温，如果是有油空压机油的参与会带走空压机压缩过程中所产生的高温，从而为机械降温。
From the structural point of view, there is no difference between the bearings of oil-free air compressor and oil-free air compressor. But from the working principle, the two have obvious differences. Oil free air compressor in the process of operation is not involved in the oil, whether it is oil-free piston machine or oil-free screw machine, they will produce a lot of high temperature in the process of operation, if it is oil-free air compressor, the oil will take away the high temperature produced in the compression process of the air compressor, so as to cool the machine.