Study on 66 patients under mechanical ventilation in ICU of Imam Khomeini Hospital in Sari.Inclusion criteria : 65-18 years old patients with at least 72 hours and maximum a week intubation, absence of acute and chronic respiratory diseases such as: COPD, emphysema, atelectasis, asthma and bronchitis and chest trauma. Exclusion criteria: pulmonary edema؛severe bronchospasm ؛ tracheostomy؛ unstable vital signs؛ hypertension؛ hyperthyroid؛ pregnancy؛ corticosteroids؛ theophylline؛ expectorants؛ mucolytics medications, bronchodilators؛ allergy history of thyme؛ rosemary and mint. Data collection was done by demographic and medical data recording questionnaires and a checklists for information of airway condition and oxygen saturation. In Intervention group for 3 days, every 8 hours 4 drops of pure thyme essential oil with 10 cc distilled water is given with nebulizer. During the day before intervention and 3 days of intervention, respiratory secretions were collected and examined for weight, volume and concentration. At 8:00 and 10:00 in the morning, 6 area of patient's lung auscultation in the supine position, and the maximum and plateau pressure of airway and oxygen saturation are noted. The control group receives 10 cc distilled water with nebulizer every 8 hours for 3 days. During one day before intervention and 3 days of intervention, respiratory secretions were collected and examined in terms of weight, volume and concentration. At 8 and 10 am, 6 area of patient's lung auscultation in the supine position, and the maximum and plateau pressure of airway and oxygen saturation will be noted.