What is the difference between positive pressure oxygen respirator and negative pressure oxygen respirator?

The main differences are:1, different levels of protection: positive pressure protection factor (safety factor) to be higher, safer to use.2, positive pressure respirator respiratory system in the pressure is always higher than the ambient pressure, negative pressure in the inhalation of the negative pressure will be generated.3, the structure of the different: positive pressure oxygen call in the positive pressure pressure generated in the structure of the pressure, negative pressure does not have.4, the technical parameters of them are different: such as rationing of the amount of oxygen, the temperature of the exhale and so on.