Professional Development for Health & Safety Experts CIH Question 05/25/2017 – Thermal Stress
An employee employee needs needs to lose 724 BTU/hr BTU/hr through evaporation evaporation in order order to maintain maintain a body body temperature of 98.6 degrees F. The outdoor air temperature is 89 degrees F and the water vapor pressure is 33.3 mm Hg with a wind speed of 14 mph. What is the heat stress index? A. B. C. D.
0.49 12.3 14.6 48.5
(Solution on next page)
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Professional Development for Health & Safety Experts
Solution: Heat Stress Index (HSI) =
x 100
Ereq = Evaporation required to maintain temperature Emax = Maximum rate of evaporative cooling Emax = (2.4)(V0.6)(42-PW a) Emax = maximum evaporative heat loss in BTU/hr V= air speed in feet per minute (fpm) PWa = vapor pressure of water at air temperature (mmHg) Convert 14 miles per hour to feet per minute.
14
x
x
= 1,232 ft/min
Emax = (2.4)(1232) 0.6(42-33.3) Emax = 1493.12 BTU/hr HSI =
/ , /
x 100 = 48.5
The correct solution is D.
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[email protected]
www.BowenEHS.com Copyright © 2017 Bowen EHS – A Division of Bowen Learning Network, Inc.
