Complex sentence: As compared to air, which contains 20.95% oxygen, higher temperatures can be reached using pure oxygen, because although approximately the same total energy is produced when burning a fuel with oxygen as with air, the lack to diluent inert gases.
Split into simpler sentences: As compared to air, which contains 20.95% oxygen, higher temperatures can be reached using pure oxygen. Approximately the same total energy is produced when burning a fuel with oxygen as compared to with air; the difference is the lack of diluent inert gases.