Ultralow NO2 module is a self-developed ultralow detection module based on experience of foreign and domestic environmental protection online monitoring as well as industrial analysis for many years. Combined with long optical path gas chamber, it adopts UV Differential Optical Absorption Spectroscopy technology with low detection limit of 0.5mg/m3. Compared with NOx converter, it solves the problem of ultralow NO2 monitoring occasion without considering that converting efficiency reduces or loses out of moisture, dust or catalyst. At the same time, it is able to provide module integration for customer who needs to add NO2 component. The module owns features of high accuracy and reliability, low operating cost, fast response speed and wide application range etc.