PROCEEDINGS of the HUMAN FACTORS SOCIETY-29th ANNUAL MEETING-I985 Zonal Differentiation of Performance Under Heat Stress

This paper details four discrete zones which describe the l i m i t of human physiological and performance capabilities in conditions of elevated environmental temperature. Boundaries t o these zones a r e expressed i n both environmental and physiological parameters. The prac t ica l appl icat ion of these zones may be real ized where individuals a r e exposed t o continuous or intermittent heat stress. INTROWCTION There a r e many circumstances i n which individuals may be exposed t o thermal stress.!&pically, extremes of heat are associated with equator ia l o r deser t regions, t he aerospace environment, or work i n heavy industry where heat sources a r e e i the r openly exposed or an i n t r i n s i c element of t he operational surround. Milder l e v e l s of h e a t a r e exper ienced i n continental or t rop ica l c l imates and a l s o i n many conf ined spaces where l o c a l a i r-conditioning is unavailable. Additionally, r e c e n t energy conse rva t ion measures have d ic ta ted t h a t occupational environments be maintained a t ambient l e v e l s approaching or violating the thresholds of the thermal comfort envelope. The o r i g i n of i n t e r e s t i n t h e re la t ionship between temperature and human behavior is founded i n an t iqu i ty (Sanctorius, 1614) but it i s t h e necessity t o operate i n these diverse and sometimes arduous thermal environments which drives contemporary concern f o r the problems of excessive hea t and cold (Hancock, 1984). With respect t o behavioral experimental research, there are four factors of particular interest. W e w i s h t o know how variation i n the thermal environment ac ts t o affect the comfort, health, safety and performance of the exposed individual. It is l i k e l y t h a t there is some c lear and definable relationship between thes