These roast with high velocity hot air flow, keeping green coffee beans suspended in the air, turning and moving in the roasting chamber.
A powerful air flow is needed at the beginning of roasting cycle for coffee beans lose density, and the air loses its velocity as roasting goes further.
Roasting and cooling are made in the same chamber in most of the fluid bed roasters. The hot chamber should also be cooled together with the roasted beans at the end of roasting which means more time and energy is required for cooling. Many roast masters using fluid bed roasters use separate cooling chambers.
Fluid bed roasters are safe and at reasonable prices. There is minimum risk of burning the bean surface.
High velocity air flow destroys the flavor and cools the heat source. Roast master should balance gas and air flow to obtain the required taste since proper bean movement is necessary for a good roast.