Abstract: A cost effective method is provided for determining empty and/or near empty medical and other medical emergency oxygen tanks employing a single, simple device for practicing the method, comprised of 5 or 6 readily obtainable components, to issue visual and audible alarms when the oxygen pressure of a medical oxygen tank has decreased to a predetermined pressure, deemed too low to provide the needed and/or prescribed oxygen flow rate to a patient to alert medical personnel and other caregivers that it is time to replace the tank in with a full tank.