A 19-year-old man presents to the emergency department with acute onset dyspnoea and pleuritic chest pain. He is tall and thin, with a background of smoking. Chest X-ray shows a 3 cm rim of air between the lung margin and chest wall at the right apex, with no mediastinal shift. He is haemodynamically stable and not significantly breathless at rest. According to current Australian guidance, what is the most appropriate initial management?