Hello DarrenC, I didn't find specific generation data, however there is an article in the Welding Journal dated August 2006 starting on page 38. It is titled "Reducing Exposure to Hexavalent Chromium in Welding Fumes", there appears to be a considerable amount of information in this article and it also gives comparative fume generation related to  various processes. Hope this helps with your quest. Regards, aevald P.S. I wanted to add a small bit of additional information. There is a lady that works out of the University of Washington in Washington state who is involved in evaluation of fume exposure evaluation and control measures. Her name is Venetia Runnion, CIH, CSP / Research Industrial Hygenist / Field Research and Consultation Group / Department of Environmental and Occupational Health Sciences / University of Washington / 4225 Roosevelt Way NE, Suite 100 / Seattle, WA 98105 / Phone: 206-543-9711 / Fax: 206-616-6240 She is working on Hexavalent Chromium issues and is collecting information for a database to do evaluation and control work. She might be able to answer some of your questions and give you additional information.