Circular diffusers are used for air distribution for both heating and cooling, typically mounted on ceilings. The blowing air stream is of an adherent (flat) type, with a multi-layer conical surface structure. Due to the indoor induced air flow being greater than the exhaust air volume, the blowing air stream decelerates quickly. For any given area, it can supply a larger air volume, and the size of the diffusion radius varies within the specified air volume range. The multi-layer conical structure is generally installed on the ceilings of heating and cooling rooms, with the blowing air stream being adherent, excellent internal induction, large air delivery temperature difference, even blowing air stream, and the ability to suppress perceived air flow. The inner blades can be adjusted in two stages (up and down) according to different air delivery conditions in winter and summer. The blowing air stream is horizontal in summer and vertical in winter and summer.