What indicates that an oxygen tank is considered empty?

An oxygen tank is considered empty when the gauge reads 500 psi or less. This gauge measurement indicates that the tank has reached a point of low pressure where the remaining efficiency of the tank for delivering oxygen is insufficient for safe usage. Generally, it is recommended to replace or refill the oxygen tank at this pressure threshold to ensure that there is adequate oxygen supply for patient needs, especially in medical or emergency situations.

Other options misinterpret the standard thresholds. For example, a gauge reading under 200 psi might imply that the tank is very low, but it is above the accepted minimum threshold for replacing the tank. Similarly, the duration of usage does not solely determine the need to replace the tank, as usage rates may vary widely depending on the specific application and flow rate. Lastly, a label marking does not provide a reliable measure of the tank's contents or safety, since it could vary based on different protocols or manufacturers. Thus, the reading of 500 psi serves as the recognized standard for assessing when an oxygen tank should be considered empty and requires action for replacement.