I've come into the possession of a Home fill II compressor and Platinum 5 concentrator. https://www.invacare.com/product_files/1100873.pdf INVACARE PLATINUM 5 SERVICE MANUAL Pdf Download | ManualsLib. And was wondering at the feasibility of using them to (slowly) create 80~90% fills. I don't think it would be too hard to adapt a fitting that would allow me to fill a scuba tank or a J. From what I could find in the manual it is rated for continuous operation which is good because I think it will take between 28 and 70 hours to fill a J. I heard that oxygen concentrators also concentrate the argon. Would this be a problem for partial pressure blending of nitrox/deco mixtures? Usually not higher that 50%. Basically what haven't I thought of or don't know, that could be a problem. I have found a few references to concentrators in threads but nothing definitive.