Until the late 1950s, virtually no firms specialised exclusively in testing, adjusting, and balancing the components of heating, ventilating, and air conditioning (HVAC) systems. The balancing, if performed at all, was done by the HVAC contractor, who lacked the necessary expertise required for advanced testing and balancing. After installation, many design engineers found that their systems were not working, not because of flawed design but because of improper balancing or deficient performance of the equipment. As a result, independent rating associations were founded by reputable members of the industry to standardise fan testing methods and develop better field testing procedures. The need for independent testing and balancing companies also became apparent.

KEYWORDS: testing, regulating, components, building services, heating, ventilation, air conditioning, engineers, performance, equipment, fans, site testing, selecting.