The oxygen-free environment in the chamber is mainly achieved by nitrogen purging: high-purity nitrogen, usually above 99.999% (oxygen requirements vary by product), is fed into the air duct, heated, passed through the filter and recirculated until the target value is reached. Oxygen content is currently measured mainly with zirconia analyzers: after power-on, the zirconia is heated to its working temperature of 700-800℃ and starts measuring.
Common oxidation-free oven specifications from Dongguan Xinzhou / Hubei Xinhai, for reference:
