The aitil of this work was to study the effect of prolonged ammonia exposure at different concentration on the pulmonary function tests im workers of El - Nasr Company of Fertilizers , Talkha - Dakahleia . It was found that ammonia has an irritant effect on the bronchial tree of exposed workers . There was a decline in vital capacity , forced vital capacity and forced expiratory volume with an increase in the forced mid expiratory flow . These changes of pulmonary functions were directly proportional to the concentration of ammonia and to the duration of exposure . Smoking intensified the effect of ammonia on the ventilatory functions