To deliver chilled air from a ceiling to the interior zones of a modern open space office, the designer has a choice of several types of ceiling-mounted air diffusers: circular or square cone, light. troffer, modular linear (or ceiling slot), and continuous linear, to name a :few. Of these, the continuous linear air diffuser has several advantages: good appearance, low first cost, excellent integration with the ceiling grid, low fan energy requirements, and the potential for extremely uniform air distribution. This type of diffuser should see increasing use because of its low static pressure requirements and the growing acceptance of the open office concept, for which it is ideally suited, by architects and builders. Therefore, it was decided to test the performance of a particular continuous linear diffuser in a simulated interior zone representing a typical open office environment. The objective was to determine under what conditions a system of these diffusers could provide both a satisfactory and an optimum air diffusion. The dependence of diffuser performance on six independent variables was determined by using values of the Air Diffusion Performance Index (ADPI) which is defined by ASHRAE as the percentage of points; measured which are within specified, draft temperature and velocity limits.