Abstract: The invention provides an inexpensive and electrically isolated remote monitoring apparatus for monitoring the operational status of any oxygen concentrator by specifically monitoring the standard set of high and low pressure diagnostic light emitting diodes provided with most concentrators. Flexible boots enclose the respective optodetectors and are forceably pushed over the diagnostic diodes of the oxygen concentrator so that any light emitted by either diode is detected by the respective optodetector. The optodetectors are further connected to a microcontroller. A telephone line interface port connects to the microcontroller and provides for a telephonic communication link between the microcontroller and a remote computer. When a malfunction is detected and analyzed by the microcontroller, both the type of malfunction and a location code is transmitted to the remote computer.