In this article, ENSR presents an evaluation tool for Radon gas monitoring programs that companies with large portfolios of properties will find useful in reducing their efforts and expenditures. The World Health Organization (WHO) considers Radon gas the second cause of lung
cancer and the first source of natural radiations affecting the human population. In Italy, Legal Decree No. 230 (0/17/95) is the laws that regulate gas Radon concentrations in work places. Hereunder we present the ENSR approach to executing preliminary geologic studies aimed at planning an instrumental monitoring program for companies.