Radsafers, I tried to find a copy of MARSSIM on the web last week. No can do. The only thing I found was an EPA site that had about 15 individual chapters and appendices as separate pdf files. Is there a pdf file on the web with the entire MARSSIM as one file? Best regards, Wes Wesley R. Van Pelt, PhD, CIH, CHP Wesley R. Van Pelt Associates, Inc.