近年来，人们越来越重视风机和系统的额定值、编目和测试，以确保其正常运行，并将能源消耗降至最低。因此，系统设计中的安全系数已降低，因此，计算的系统阻力或风机性能中几乎没有误差。因此，至关重要的是，那些可能影响风扇性能及其影响程度的项目，应成为我们常识的重要组成部分。 多年来，人们已经知道，在实验室测试的风机一旦安装在现场，可能不会执行相同的操作。已经有几篇文章描述了这些现象。该项目旨在更详细地解决实验室风扇额定值与现场条件下获得的实际性能之间的差异问题。现场安装条件，包括管道系统组件的具体位置和设计，可能会影响风扇的性能。 这些因素不仅影响流量和风扇静压”，还影响风扇制动马力。

In recent years there has been increased emphasis placed upon the rating, cataloging, and testing of fans and systems to assure their proper operation and to minimize the consumption of energya As a result, safety factors in system design have been reduced so that there is very little allowance for error either in the calculated system resistance or the fan performance. It is, therefore, essential that those items which can affect fan performance and the magnitude of that, effect become an important part of our general knowledge.It has been known for many years that a fan tested in the laboratory may not perform the same once it is installed in the field. Several articles have been written which describe these phenomena. This project was initiated to address the problem, in much greater detail, of variations between laboratory fan ratings and the actual performance obtained under field conditions. Field installation conditions, including the specific location and design of ductwork components, can affect a fan's performance. These elements influence not only the flow rate and fan static pressure, "but also the fan brake horsepower.