A fluid-bed roaster works by pushing hot air across coffee beans. The roast chamber is filled with heated air provided by a small fan and heating coil located beneath the chamber. In a fluid-bed roaster, the flow of air is both the heat source and the mechanism responsible for agitating the beans. Since air is the heat source, heating happens via convection, rather than via convection and conduction, as in a drum roaster. Fluid-bed roasters are generally less expensive than comparable drum roasters, and they produce a bright flavor profile. This type of roaster works well with small size batches (under half a pound).