Chrysler Repair: ask OFN auto air conditioning (in general), commercial refrigeration units, auto air conditioning

Question
Hi, Mr. Roland Finston! I'd like to know what means the expression " break each vaccum with OFN"?

Thanks.

Answer
Hi Sergio,
I have not seen the term OFN used in auto air conditioning but I did a Google search and it appears to be a contaminant of some sort that is discussed in the business of commercial refrigeration units. Could it possibly mean 'old freon', i.e. R-12? I wish I could offer you more but you might ask the question to a commercial (e.g. building) air conditioner repair person.
Roland