Conference Contribution Details


RM Gee, SA Bell, RE Imhof, M Stephens, P Xiao & the TEWL Calibration Consortium.
Contributed Talk, 5th International Symposium on Humidity and Moisture. Rio de Janeiro 2006.



Transepidermal water loss (TEWL) is the rate of water vapour loss through skin, and is an indicator of skin barrier function. This is important in medical care, in occupational monitoring against skin damage, and in dermatological research. TEWL is evaluated by measuring the water vapour flux from the skin surface using instruments which incorporate relative humidity sensors. However, TEWL instruments of different types can give results differing by as much as 50 percent of reading, due to the lack of a harmonised and traceable method of calibration. A new calibration method for TEWL instruments has been developed using evaporation of a droplet of water of known mass. A variety of water vapour flux rates can be generated, so that TEWL instruments can be calibrated at several values in the range of operation.

This paper details the sources of uncertainty in TEWL measurement and calibration. Some types of error can affect only calibration, while others can occur in subsequent use of the instrument. Certain of these apply differently to the different designs of TEWL instrument available. An uncertainty analysis is presented for the TEWL calibration process under these varying conditions, and for a range of TEWL values.


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