The present research opens a series of experiments designed with the intent of better understanding the dangers to warm blooded animals and thus to man, of fluorinated gaseous substances used at the Fluoroderivative Research Center DIRI. This work contains references to results obtained with perfluoropropene of high purity (Titer 98.5% by volume, from Spinnetta). We selected as a biological test the albino rat, both because this animal shows an intermediate sensitivity to fluorine derivatives among the various species and because it was suggested by the majority of authors working in this field of experimentation. Acute exposures were carried out at 50, 250, 500, 5,000 and 50,000 ppm for periods, in general, of 2 and 5 hours. Each group of animals consisted of 2 males and 2 females maintained without food for an hour before treatment until the end of the period of exposure.