Figure 9-32 The U.S. Food and Drug Administration negative-pressure leak test. A negative-pressure leak-testing device is attached directly to the machine outlet (left). Squeezing the bulb creates a vacuum in the low-pressure circuit and opens the check valve. When a leak is present in the low-pressure circuit, room air is entrained through the leak, and the suction bulb inflates (right). (Adapted from Andrews JJ: Understanding anesthesia machines. In 1988 Review Course Lectures. Cleveland, International Anesthesia Research Society, 1988, p. 78.)