Recently, there has been an unexpected upturn in the field of fans, attributed to the solution of various fluid dynamics problems. The development has been so rapid that a efficiency of 90% has suddenly been achieved in a compact design. As a result, the previously overlooked group of machines has gained significant interest, which is also reflected in translations of the book into several foreign languages. It seems to be the right time to present the entire field in a concise manner. I have revised much, removed some unnecessary content, and included numerical results from new experiments for practitioners. Significant expansions have been made in small blowers and cross-flow blowers. The important physical principles have been discussed in greater detail.