Nitrogen is usually a colourless and odourless gas， and it is generally less dense than air. Nitrogen is chemically inactive and hardly reacts with other substances at room temperature， so it is often used to make preservatives. However， under high temperature and high energy conditions， it can undergo chemical changes with certain substances and be used to produce new substances useful to human beings. Due to the chemical inertness of nitrogen， it is often used as a protective gas， such as: fruits and vegetables， foodstuffs， light bulb filling gas. In order to prevent certain objects exposed to air oxidised by oxygen， filling grain silos with nitrogen can make the grain not mouldy， not germinate， long-term preservation.

Liquid nitrogen can also be used as a deep freezing agent. As a freezing agent， it is often used in hospitals to remove spots， bags， beans， etc.， so that the spots， bags， beans， etc.， can be frozen off， but scars are likely to appear， and its use is not recommended. High-purity nitrogen is used as a carrier gas for chromatographs and other instruments. It is used as a protective gas for bright annealing of copper tubes. Together with high-purity helium and high-purity carbon dioxide， it is used as a laser gas in laser cutting machines. Nitrogen is also used as a protective gas for food preservation.

In the chemical industry， nitrogen is mainly used as a protective gas， replacement gas， and scrubbing gas. It is used as a protective gas for reflow and wave soldering to improve the quality of soldering. It is used as a protective gas in the production of float glass to prevent oxidation of tin baths. Although nitrogen is a very common inert gas， but its application is very wide， the use of different ways， the requirements are also very different. For example， if it is used as a loading and purging gas， ordinary nitrogen can be used， but if the process equipment has higher requirements， higher grade clean fittings are needed.