Appologies to RADSAFE I can't seem to reply direct to Chris Davey. Chris if you haven't received an answere with a good source. NCRP 105 has a list of precautions for lab personnel which includes knee length lab coats. If you need specifics send me a message @ vernig.peter@forum.va.gov or call 303-399-8020 ex 2447. Peter G. Vernig, VA Medical Center Denver, Co, USA