Try contacting your local Factory Mutual Office for clarification and advice. T hey virtually write the fire codes, so may be of help. An engineer that we work with here is Trudy Zedaker Yarger, 313-540-0500. She is very practical and ver very helpful. Give her a call and I am sure that she can help or refer you to t he right place & person. Geoffrey Brown Kelsey Museum University of Michigan [log in to unmask]