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|Title: ||Clothing ventilation and human thermal response|
|Authors: ||Bouskill, Lisa M.|
|Keywords: ||Thermal insulation|
|Issue Date: ||1999|
|Publisher: ||© Lisa M. Bouskill|
|Abstract: ||Given the importance of heat balance being maintained between a person and their environment
an appropriate clothing choice is essential. Since military personnel are required to work
effectively when deployed in any of the world's climates it is important that the thermal
protection afforded by their clothing is considered as well as its more obvious protective
properties such as those relating to the chemical and abrasive environments.
Clothing descriptions restricted to details of heat and water vapour transfer characteristics
alone, as is commonly the case, are recognised as being insufficient. Of particular note, where
these data are obtained under 'artificial' conditions, ie intrinsic values, they are unlikely to
represent the 'resultant' values as observed when worn by human subjects engaged in actual
work tasks. Where intrinsic data are used in predictive standards calculations, to estimate safe
work times etc, the workforce under consideration may not always be protected.
One source of change in the thermal properties of clothing, when in the workplace, occurs due
to increased convective and evaporative heat transfer at the wearer's skin surface caused by air
movement through the clothing. This may occur as a result of wearer body movements or
increased environmental air speed. The Ventilation Index has previously been suggested as an
accurate and repeatable method for quantifying clothing ventilation characteristics. Although
several other measurement techniques have also been suggested, the Ventilation Index is simple
(albeit laborious) to conduct, and does not require the use of expensive equipment. Work
conducted towards this thesis has shown that the Ventilation Index may be suitable for use in
either manikin testing or human studies assessmentso f clothing.
The aim of this thesis was to investigate the suitability of the Ventilation Index as a
measurementt echnique for the assessmenot f clothing ventilation characteristics, particularly to
consider the relationship between clothing ventilation and wearer physiological responses and to
identify the factors which can affect this. The Ventilation Index measurement systems
constructed as part of this research have improved on those used previously in similar research.
New materials technology has provided an improved air-tight oversuit for use during
measurement of the clothing micro-environment (a constant source of fiustration, it appears, for
previous authors), while extensive calibration of the whole system has proved its accuracy.
Using the Ventilation Index has shown that the ingress and egress of air into and from the
clothing micro-environment may induce a physiological response from the wearer of the
clothing (chapter 6) such increases in air movement being reflected by a drop in insulation
afforded by the clothing (chapter 7). Of particular interest to persons involved in the thermal
assessment of clothing, will be the suggestion that clothing may exhibit different ventilation
characteristics when tested on a thermal manikin to when worn by human subjects. This
difference appearing to be related to clothing fit (investigated in chapter 9). Of interest to
wearer's of protective, is the observation that air-impermeable clothing does not necessarily
withstand changes in environmental air movement (chapter 10).
The technique is not without criticism. The standard tracer gas technique, used to calculate
clothing air exchange rate, considers only air movement occurring next to the wearer's skin. In
multi-layer clothing ensembles, the movement of air in clothing layers more distant will change
the clothing micro-environment and thus have consequences for the wearer. Preliminary
investigation suggests that distribution of nitrogen to each clothing layer should enable
assessmenot fair movement in each of these layers.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Design School)|
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