Thermal responses at three low ambient temperatures: Validation of the duration limited exposure index

Abstract The objective of the study was to validate the DLE (duration limited exposure) index, which provides a method to determine acceptable time limits when, in a cold environment, clothing insulation is not sufficient to protect the wearer from body cooling. The thermal responses of ten male subjects dressed in winter clothing to −6, −14 and −22°C during very light exercise were studied. The individual variation of peripheral temperature responses was large. The majority of the subjects stated that they would accept the exposure once a day, but not continuously. DLE was on the `safe side' according to the body net heat debt and rectal temperature, but at the same time it allowed for low skin temperatures, especially of the extremities at low ambient temperatures. At predicted time limits, the mean skin temperature criteria of DLE suggested in the ISO document ISO/TR 11079 were not met at −14 and −22°C. Introduction of limit criteria for extremity cooling in prediction models would render a more complete assessment of cold stress. Relevance to industry Since the protective clothing worn by the worker is not always sufficient for the actual low ambient temperature there is a need for accurate predictions of exposure time.