In this episode, Dr. Steven Haywood discusses the critical importance of allowing patients to exhale properly during non-invasive ventilation (NIV). He explains the differences between old school invasive mechanical ventilation with a two-limb circuit and modern NIV systems with a single limb, highlighting the necessity of exhalation ports to prevent mechanical and physiological dead space. Haywood elaborates on the evolution of mask designs, particularly how vented masks became essential for severe COPD and asthma exacerbations but posed challenges during the COVID-19 pandemic, leading to a switch back to non-vented masks with viral filters. He emphasizes the physician's responsibility to ensure the correct use of equipment to avoid patient harm and concludes with advice on selecting appropriate masks and ventilators for non-invasive ventilation.