Air sensitivity is a term used, particularly in chemistry, to denote the reactivity of chemical compounds with some constituent of air. Most often, reactions occur with atmospheric oxygen (O2) or water vapor (H2O), although reactions with the other constituents of air such as carbon monoxide (CO), carbon dioxide (CO2), and nitrogen (N2) are also possible.
The range of methods used to work with air-sensitive compounds are known as air-free techniques. Two main methods exist — gloveboxes and Schlenk lines. Gloveboxes are sealed cabinets filled with an inert gas such as argon or nitrogen. Normal laboratory equipment can be set up and manipulated through the use of the gloves. A Schlenk line is a vacuum and inert-gas dual-manifold that allows glassware to be evacuated and refilled with inert gas.