Tension pneumothorax is a life threatening complication of chest injury. It can cause rapid physiological decompensation, cardiac arrest and death. The Joint Royal Colleges Ambulance Liaison Committee (JRCALC) provide guidelines on the pre-hospital diagnosis and treatment of this condition. This Continuing Professional Development (CPD) module firstly looks at the pathophysiology of the developing tension pneumothorax, discusses the signs and symptoms likely and less likely to be found, looks at the difficulties in recognising these signs and analyses the accepted methods of first line treatment. The module goes on to study alternative pre-hospital management methods and discusses the safety and effectiveness of each.