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There are many situations in which it might not be possible or economical to control the entire environment of a space for the maintenance of the thermal neutrality and comfort of its occupants. As a practical solution to this problem, an investigation was undertaken at the Institute for Environmental Research of Kansas State University to explore the possibility of relieving heat stress in hot environments by ventilating the heads of subjects, frontally,with a jet of cool air. Azer et al.(1972) conducted an investigation in which localized ventilation was applied frontally to the heads of three different groups, six subjects each, while they were seated in hot environments. One group was tested in a 90 F and 71% environment; the second was tested in a 95 F and 50% environment; the third, in a 100 F and 34% environment. These three environments have the same Effective Temperature (84.9 F). The Effective Temperature (ET) as defined in ASHRAE Handbook of Fundamentals (1967) is an empirical index combining in a single value the thermal effects of temperature, humidity and air movement upon the human body. Each subject tested appeared twice. In one appearance he performed the test in the hot environment without localized ventilation; in the other he was exposed to the same environment but with localized ventilation. The duration of each test was 125 minutes. Without localized ventilation, the subjects' average thermal sensation was between warm and hot, and their comfort sensation was between uncomfortable and very uncomfortable. It was possible to improve both sensory votes, moving them towards "thermal neutrality" and "comfortable" sensations, by locally ventilating the head. The ventilating jet had a temperature 50 F, a velocity 750 fpm, and a relative humidity 50% at its outlet. The outlet diameter of the jet was 2.5 in. and the outlet was located 15 in. from the subject's face. The improvements in sensory votes were associated with reductions in average skin temperature, rectal temperature, heart rate, and sweat rate from their corresponding values measured during experiments without localized ventilation. From these experiments it was concluded that more tests were needed to determine the effectiveness of localized ventilation in relieving heat stress in other heat stress environments.

The objective of the present paper is to report the results of an experiment in which localized ventilation was applied to a group of six subjects while being exposed to a 95 F and 75% environment. This environment has an ET of 89.9 F. A~cording to MacPherson (1960), this environment represents an extreme heat stress environment which can be tolerated by non-acclimatized healthy men wearing light clothing and engaged in very light activities for a few hours.