Tension pneumothorax is a life-threatening medical emergency condition that can occur with chest trauma and is more likely to happen with trauma involving an opening in the chest wall & sometimes due to rupture lungs bulla in case of emphysema / COPD. Recognizing and treating it quickly is important. Tension pneumothorax is the progressive build-up of air within the pleural space, usually due to a lung laceration which allows air to escape into the pleural space but not to return. Positive pressure ventilation may exacerbate this ‘one-way-valve’ effect. Progressive build-up of pressure in the pleural space pushes the mediastinum to the opposite hemithorax, and obstructs venous return to the heart. This leads to circulatory instability and may result in traumatic arrest. The classic signs of a tension pneumothorax are deviation of the trachea away from the side with the tension, a hyper-expanded chest, an increased percussion note and hyper-expanded chest that moves little with respiration. The central venous pressure is usually raised, but will be normal or low in hypovolaemic states. However these classic signs are usually absent and more commonly the patient is tachycardic and tachypnoeic, and may be hypoxic. These signs are followed by circulatory collapse with hypotension and subsequent traumatic arrest with pulseless electrical activity (PEA). Breath sounds may be very difficult to appreciate and misleading in the trauma room. Tension pneumothorax may develop insidiously, especially positive pressure ventilation. This may happen immediately or some hours down the line. An unexplained tachycardia, airway pressure are strongly suggestive of a developing tension. Treatment include immediate oxygen support & urgent (intercostal drainage)