Figure 9-15 Simplified schematic drawing of the Ohmeda Tec-type vaporizer. At high temperatures, the vapor pressure inside the vaporizing chamber is high. To compensate for the increased vapor pressure, the bimetallic strip of the temperature-compensating valve leans to the right, allowing more flow through the bypass chamber and less flow through the vaporizing chamber. The net effect is a constant vaporizer output. In a cold operating room environment, the vapor pressure inside the vaporizing chamber decreases. To compensate for the decreased vapor pressure, the bimetallic strip swings to the left, causing more flow through the vaporizing chamber and less through the bypass chamber. The net effect is a constant vaporizer output. (Modified from Andrews JJ, Brockwell RC: Delivery systems for inhaled anesthetics. In Barash PG, Cullen BF, Stoelting RK [eds]: Clinical Anesthesia, 4th ed. New York, Lippincott-Raven, 2000, pp 567–594.)