Hi PhylissD, and thanks for this question. In my professional experience, oxygen concentrators dispense only oxygen that is suitable for the medical arena. If someone requires supplemental oxygen, it is best that it be prescribed by a physician and provided by a reputable medical equipment supplier. Should a patient/person choose to buy a device without the prescription of a physician, there is no medical support system in place to insure the equipment is suitable and safe for home use. As well, using supplemental oxygen without the guidance and oversight of a physician can be unsafe indeed!
When it comes to cylinder oxygen - there is a distinct difference between medical and commercial/industrial grade. It has to do specifically with the purity of the oxygen content of the cylinder. This is critical to keep in mind.
I hope this brief answer has provided you with the information you need.
All the best, Leon (site moderator)