Creating Nitrox with Partial Pressure Fills
All cylinders and valves used for partial pressure fills must be oxygen cleaned and maintained perfectly clean to prevent an oxygen fire from occurring. There have been quite a few oxygen fires in dive facilities and home filling stations. They are very serious accidents and divers have been maimed and killed. There are many good articles on the web. I strongly suggest you study the following and do more research on your own. The major training agencies have good formal courses on partial pressure filling.