As flueless gas fires do not rely on a chimney, they provide an unsurpassed level of safety to which flued fires can only aspire. Flues and chimneys can become blocked or adversely affected by down-draughts. flueless gas fires are designed to burn the gas extremely cleanly without a flue. The burnt gases are then passed through a catalytic converter. Every flueless gas fire has an oxygen depletion sensor which constantly monitors the air quality in the room. If the level of oxygen drops by just 1.5%, the fire automatically shuts down.