Mapleson D (Bain) circuit

Bain circuit (a modified Mapleson D circuit) attached to a contemporary anesthesia machine auxiliary common gas outlet. The green knob is the adjustable pressure limiting (APL) valve, and the blue hose leads to the scavenger system.
​The anesthesia machine's circle breathing system and ventilator, seen in this photo, are not used when the Bain circuit is attached. The circle breathing circuit can be recognized by its domed unidirectional valves, breathing hose connectors, black APL valve, carbon dioxide absorbent canister, and selector switch. The ventilator can be recognized by its bellows. The inspiratory and expiratory hoses for the circle breathing systems are not shown in this photograph.