In order to minimize the wind noise generated by a Sirocco fan, it is most important to understand the details of the flow field about a Sirocco fan. As the shape of a Sirocco fan is very complicated, it has not been very easy to capture the flow patterns about a Sirocco fan. Presently, the authors have utilized the spark tracing method to visualize the flow field around a Sirocco fan and have observed the inflow patterns with and without the intake load. It has been proved that the intake load causes the drastic changes on the inflow pattern and thus the changes of the flow pattern in the scroll chamber. These changes might be the major cause of the wind noise of a Sirocco fan operating under the intake load. Moreover, applying the DP matching technique to the obtained images, the quantitative velocity components have also been calculated.