While rare, anesthesia breathing system obstruction can have devastating consequences. We created simulated occlusions of the expiratory and inspiratory limb of the circle breathing system in 3 current anesthesia workstations; Aisys, ADU (both by GE Healthcare, Madison WI), and Apollo (Draeger Medical, Telford, PA). The automated electronic checkout specific to each machine was then performed. The Aisys allowed users to accept both faults and initiate simulated patient care; the ADU and Apollo did not. Users must be aware of how to test for breathing circuit obstruction, and whether their own equipment does so adequately in the automated checkout.