The air outlet is a circular diffuser, which is generally used for cooling and heating air supply, and is usually installed on the ceiling. The blowing airflow is attached (flat delivery) type. Its structure is multi-layer cone type. Since the indoor induced air flow is relatively larger than the exhaust air volume, the blown air flow decelerates faster. Therefore, a larger air volume can be supplied relative to an area of any size, and the variation of the diffusion radius within a given air volume range is small.