On construction sites where asbestos is present, diseases due to its exposure are already known because it is a fine and sharp fibre that can cause various diseases such as lung cancer, pleural plaques and malignant mesothelioma, gastrointestinal cancer, ovarian cancer, bladder cancer, skin cancer, liver cancer and kidney cancer, among other types of diseases. This study will analyse the legislation in force and give an example of its application on site. Regarding the rehabilitation of buildings with asbestos, it is necessary to prepare a procedure sheet, according to the stipulations of Decree-Law No. 266/2007 of 24 July, since there are increased risks for the workers involved in the work. It will be described the most relevant and mandatory aspects on site, so that a rehabilitation work can be carried out safely and in compliance with all the legislation in force, taking into account the aspects of safety and health. In this work, it was possible to obtain a concentration of the fibres present in the atmosphere through the phase contrast microscope, verifying that it was far from exceeding the exposure limit value indicated in DL No. 266/2007 of 24 July, with presentation of examples of application on site, complying in terms of safety and health with the legal parameters of exposure levels.