I think that from what I have heard the use of Benzatriazole in the Amidol formula, for use with Azo, has to do with the age and place of manufacture of the Azo paper. Grade two Azo is currently manufactured at the new plant in Canada with a corresponding new emulsion (wouldn't you know this about Kodak...take a good thing and change it). The grade three Azo is also manufactured in Canada with no change in emulsion. Grade two Azo is the paper that some people are incorporating Benzatriazole with the Amidol formulation.