Oxygen conservers allow patients to carry smaller cylinders since the oxygen is pulsed to the patient on inhalation rather than offering a continuous flow of oxygen. The savings ratio stated with most conservers is based on a comparison to continuous flow use. For example, 3:1 savings means with the use of a pulse dose conserver the cylinder will last 3 times longer than when used in a continuous flow setting. This is ideal for conserving oxygen since the gas is needed only on inhalation. Continuous flow can be wasteful and costly.