Purpose: During fiberoptic cable production gases such as chlorine, helium and freon are mainly used, and when gas leakage occurs, the workers are exposed to these gases. Chlorine inhalation causes chest thightness and dyspnea. Depending on the intensity of exposure, this can lead to different conditions varying from slight bronchial irritation to obvious pulmonary edema. We aimed to search the effects of gas leakage on the workers pulmonary function (PF) at the Fiberoptic Cable Factory. Material and Methods: The study was performed on a total of 43 workers who answered an inquiry with regard to their respiratory symptoms. In all the workers physical examinations were carried out and their chest radiography were obtained and the pulmonary function (PF) of 27 cases (Group-I), who could have been exposed to gas inhalation along with the PF of 16 control cases (Group-II; without any exposure) were evaluated. Results: Mean age of the workers was 29.7±5.0 years. In Group-I, there was chest tightness in three of the workers after exposure to the chlorine gas; in one after smoking; in two after returning to work from their vacation. When the chlorine gas amount inside the factory was 0.4 ppm, mean PF in Group-I was lower than that of Group-II; the difference was not statistically significant (FEV1/ FVC in Group I and II was %83±14 and % 88±12 respectively, p>0.05). In 30% of all cases studied, symptoms related to chronic bronchitis were positive. The ratio of smoking in both groups was similarly high (Group-I 77.8%, Group-II 56.3%). Conclusion: These findings strongly suggested that smoking was the primarily responsible agent for the symptoms in the labourers. However, in Group-I the low FEV1/ FVC ratio may also be due to the exposure to chlorine gas. Since long term damage caused by chlorine gas exposure also increases by cigarette smoking, a special effort should be undertaken to encourage the labours to quit smoking in similar factories.