Nitrogen bottle is also an indispensable tool for air conditioning maintenance. Because nitrogen is almost inert diatomic gas, its chemical property is extremely inactive, its gas molecule is larger than oxygen molecule, and it is not easy to expand in heat and contract in cold, and its deformation range is small. Therefore, before filling refrigerant, nitrogen should be used for pressure test, leak detection and flushing of the refrigeration system.

Nitrogen cylinders for storing nitrogen are generally made of steel, and other non-corrosive gases can be stored as long as they do not exceed the specified pressure. Generally, 2L is used for air conditioning maintenance; 4L； 8L； 10L these relatively small gas cylinders. Generally, the color of the nitrogen bottle is all black, and it is equipped with a pressure reducing valve and a gas pipeline. The pressure reducing valve is equipped with a high-pressure meter and a low-pressure meter.