If this is an inhouse process you will have to document a procedure to accomplish this and have it on record. If you are purchasing the gases you can work with your supplier.
Everyone of the gas suppliers that we worked with had detailed instructions on cleaning existing and new lines.
These procedures may have been codified by now as there was some talk several years ago about doing this.
Do a search on this site.
Come back with your loaction/jurisdiction and someone will be able to tell you what rules you may or may not fall under.
A little about your process conditions will greatly help.
Oxygen systems must also be extremely clean....As I recall, the Compressed Gas Association publishes guidelines on piping system design, construction and commisioning.
I recently had this same problem, and there are much safer chemicals on the market now. I don't want to recommend any, because I have very little experience, but if you contact your O2 supplier for a recommendation on how to clean for your application, they will help. Be careful reading old literature on this subject, I found some literature recommending carbon tetrachloride, which will clean very well, but you also can't use it in most places, and shouldn't want to in the rest.
