A heater for a window of an optical gas sensor is provided. The heater may be positioned over a portion of the window or may form at least a portion of the window. Alternatively, the heater may be separate from the optical gas sensor and positionable over the window either in contact therewith or in close proximity thereto. In one embodiment, the heater is substantially transparent to the relevant wavelengths of electromagnetic radiation that are used in optical monitoring of respiratory gases, anesthetic agents, or the like. Alternatively, the heater may be configured so as to provide a substantially unobstructed optical pathway through the window. Optical gas sensors and complementary transducers that include the heater are also disclosed.