A few years back i had a conversation with a technical engineer who was into his refrigerants. He suggested that the molecular size of R410a (or at least its components) was smaller than a molecule of OFN. He advised using helium to pressure test rather than OFN as it would find any leaks. I have asked equipment manufacturers, BOC, and other people and have not had a straight answer from anyone, the most common answer being, well we have always used OFN and not had any problems.

SO, was the techi correct, but the need to use helium to small to worry about?

For info i am currently employed by a large Japanese manufacturer and get the same vague answers everyone else have given. Am i flogging a dead horse?

Thanks