The Expiratory Filter Heater is designed to warm the surface of a filter used in the expiratory pathway of a breathing circuit. The device is intended to prolong filter efficiency by minimizing excessive condensation that can cause expiratory resistance. Adding a heated filtration system to a ventilator can also protect the exhalation system and currounding environment from contamination which prevents the spread of infectious diseases. The heater consists of an aluminum heating surface that is thermostatically controlled to maintain an ideal temperature.