FVC test represents a preliminary test used to approach the 2nd diagnostic level of non invasive screening in occupational pneumopathy (DLCO, N2 wash out, closure volume). Quality, validity and ability to be replicated of the test in spirometry have been evaluated. Results have been examined by Fisher exact test and by linear regression analysis. It was possible to demonstrate the validity and reproducyibility of this simple, diagnostic and non invasive screening in Occupational Health.