Air controls located on the top of the spa perform different operations. The smaller valves are called “air venturi valves”, and they affect the area around the valve itself. These controls will open an air line into the jet stream which will pull in air bubbles, thus increasing the pressure at that jet introducing bubbles into the flow.
Rotating this control will manage the amount of air to let into the stream and can be customised to your liking. These controls are directly linked to the heated air blower line, and if your spa has one (Canadian Spa models: Victoria, Niagara, Alberta, Halifax, Montreal) you will enjoy warm air bubbles as opposed to the outside air that would have been used.