What is the most common way O2 is prescribed for medical use?

Oxygen (O2) is most commonly prescribed for medical use through fractional distillation. This method is preferred as it allows for the efficient separation of oxygen from air, which comprises approximately 21% oxygen, 78% nitrogen, and 1% other gases.

In fractional distillation, air is first cooled and liquefied, then heated gradually. As the mixture warms, gases with lower boiling points, such as nitrogen, evaporate first. At higher temperatures, oxygen can be distilled and collected. This process is industrially viable and yields high-purity oxygen suitable for medical applications. It ensures that the oxygen provided to patients meets the strict standards required for safety and efficacy.

The other methods mentioned, such as chemical synthesis, thermal decomposition, and biological fermentation, are not practical or common for producing medical-grade oxygen. Chemical synthesis typically produces other gases rather than pure oxygen, while thermal decomposition is rarely used on a large scale for medical oxygen due to inefficiency and the need for significant energy input. Biological fermentation is unrelated to oxygen production; it primarily involves microbial metabolic processes that produce various byproducts, typically in the context of ethanol production rather than oxygen generation.