2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
HEAT AND MOISTURE TRANSMISSION OF CHEMICAL AND
BIOLOGICAL CLOTHING AND ITS PHYSIOLOGICAL IMPACT
Joanne N. Caldwell 1 , Yvonne C. Williams 1 , Mark J. Patterson 2 , Nigel A.S. Taylor 1
1 Human Performance Laboratories, University of Wollongong, Wollongong, and 2 Defence
Science and Technology Organisation, Melbourne, Australia
Contact person: nigel_taylor@uow.edu.au
INTRODUCTION
Within environments that pose either a chemical or a biological threat to workers, the ability
to regulate body temperature is adversely affected by the need to wear personal protective
ensembles. These chemical and biological (CB) protective ensembles impede the loss of
metabolically-generated heat, the wicking of sweat and the removal of water vapour resulting
from the evaporation of sweat. The design objective of most newly-developed materials is to
facilitate heat loss, whilst retaining the appropriate chemical and biological protection. In this
project, the focus was upon the physiological impact of exercising in a hot-dry environment,
whilst wearing CB protective ensembles made from various combinations of these materials.
METHODS
Seven physically-active males participated in this project, completing four experimental trials,
each with a different configuration of CB protective clothing. Trials differed only in the type
of CB clothing worn, which varied in the heat and moisture transmission ratings. Both the
subjects and researchers were blind to these qualities, and the ensembles were coded
alphabetically (A, B, C and D (a commercially-available CB ensemble)).
Within each trial, subjects completed external work at two intensities, which were designed to
simulate the approximate total metabolic heat production expected during vehicular activities
(e.g. aircraft flight, driving armoured vehicles). For 60 min, subjects worked at a very-light
external work rate (25 W: total metabolic heat production ≈180 W), followed by 60 min at a
light intensity (50 W: total metabolic heat production ≈300 W). All trials were performed in a
hot-dry environment (40°C, 30% relative humidity), which was based on the conditions
expected within tanks, and possibly helicopters, during 6 months of the year in Darwin
(northern Australia).
Physiological data were collected continuously, whilst psychophysical data were collected
intermittently. The former included: body core and skin temperatures, heart rate, whole-body
sweat and evaporation rates. Psychophysical indices were: perceived exertion, thermal and
skin wetness perception, and clothing, thermal and skin wetness discomfort.
RESULTS
Three principal observations arose from the current experimental series. First, the existing CB
protective ensemble appeared to more adversely affect physiological function than any of the
newly-developed garments (Table 1). This was most evident for core temperature, mean body
temperature, heart rate and the evaporation of sweat from within the ensemble. Indeed, the
new ensembles appeared to better support the attainment of thermal and cardiovascular steady
states during very-light work in hot-dry environments. This was not possible with the existing
ensemble, which would appear to impose approximately 15% greater thermal insulation than
each of the other ensembles. Indeed, from independently derived, sweating hot-plate data, the
average thermal resistance of ensembles A-C was found to be only 66% of that obtained for
ensemble D (0.036 versus 0.054 m 2 .K.W -1 : Defence Science and Technology Organisation).
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