A 32-year-old tall, slim man presents with sudden onset pleuritic chest pain and shortness of breath. He has no past medical history and is a non-smoker. Examination reveals reduced breath sounds over the right hemithorax, hyper-resonance to percussion and no tracheal deviation. A chest x-ray confirms a right primary spontaneous pneumothorax occupying 20% of the hemithorax; he is haemodynamically stable with minimal breathlessness. What is the most appropriate management?