High nitrogen purity PSA nitrogen generator plants allow production of high-purity nitrogen from air, which membrane systems are unable to provide - up to 99.9995% nitrogen. This nitrogen purity may also be ensured by cryogenic systems, but they are considerably more complex and justified only by large consumption volumes. The nitrogen generators use CMS (carbon molecular sieve) technology to produce a continuous supply of ultra high purity nitrogen and are available with internal compressors or without. Low operating costs By substitution of out-of-date air separation plants nitrogen production savings largely exceed 50%.[citation needed] The net cost of nitrogen produced by nitrogen generators is significantly less than the cost of bottled or liquefied nitrogen. Nitrogen Generators Create Less Impact on the Environment Generating nitrogen gas is a sustainable, environmentally friendly and energy efficient approach to providing pure, clean, dry nitrogen gas. Compared to the energy needed for a cryogenic air separation plant and the energy needed to transport the liquid nitrogen from the plant to the facility, generated nitrogen consumes less energy and creates far fewer greenhouse gases.