What method is used to produce small quantities of concentrated oxygen?

The method used to produce small quantities of concentrated oxygen is physical separation from air. This process typically involves methods such as pressure swing adsorption (PSA) or membrane technology, where air is passed through a material that preferentially absorbs nitrogen, allowing oxygen to be extracted in a concentrated form. This technique is efficient for generating oxygen in smaller quantities and is commonly utilized in medical settings, particularly where immediate access to concentrated oxygen is needed.

In contrast, fractional distillation is more suited for large-scale production of gases, as it separates components of the air based on their different boiling points, which is not ideal for small-scale applications. Boiling water produces steam rather than oxygen, and combustion of hydrocarbons primarily generates carbon dioxide and other byproducts, not oxygen. Thus, physical separation from air is the most applicable method for producing concentrated oxygen in smaller amounts.