Using a thermal manikin to determine evaporative resistance and thermal insulation – A comparison of methods

Abstract

Heat transfer from the human body, especially through the evaporation of sweat from the skin, is often restricted when protective clothing is used, which may result in overheating. For this reason, it is important to consider the parameters of protective clothing as input data in physiological models, such as predicted heat strain. The two most important parameters are thermal insulation and evaporative resistance with clothing area factor strongly influencing both. These parameters were determined for two clothing ensembles using a (dry) non-sweating thermal manikin. First, the clothing area factor was determined using the photographic method. Second, thermal insulation was measured in both static and dynamic conditions, and multiple equations for predicting dynamic thermal insulation from static ones were evaluated. Third, methodology for measuring evaporative resistance based on pre-wetted skin was adopted and multiple corrections were assessed. Finally, sensitivity analyses were completed using PHS to determine the impact of different equations on the duration limited exposure. For the thermal insulation measurements, we found that predictive equation (32) from ISO 9920 was the most accurate, but choosing the correct equation for protective clothing proved challenging. Although a manikin’s surface temperature is widely used for calculating evaporative resistance, the skin temperature should be used instead, since it is correct from a physical point of view and there is a difference of up to 15% in the results. Because these measures are used in thermal risk analyses conditions, a high degree of accuracy and a knowledge of the inputs must be guaranteed.

Common clothing area factor estimation equations are inaccurate for highly insulating (<b><i>I</i></b>_cl>2 clo) and non-western loose-fitting clothing ensembles

“…**SK is the textile skin that was used only during evaporative resisitance measurements. shows the total and basic insulation 19 ) and total and clothing evaporative resistance 20 ) of selected clothing combinations, and the measured f cl . The full details of the measurements, and description of the clothing items and the ensembles is available in Kuklane and Toma 19 ) .…”

“…Table 1. f cl from photographic method, total and basic clothing insulation, and total evaporative resistance and clothing evaporative resistance of selected clothing combinations (for methodological background see Kuklane et al 29) , Toma et al 30) , Toma et al 31) 19) . T1 T2 T3 T5 T4 T6 T8 T7 T9 T14 T10 T11 Comparison of estimated and measured f cl of cold protective clothing from various published studies where f cl by photographic method was available 6,19) and from some unpublished data sets.…”

Applicability of Human Thermophysiological Model for Prediction of Thermal Strain in PPE

“…The total thermal insulation of clothing IT and local thermal insulation IT,i were measured using a standard procedure according to EN ISO 15831 [26] and calculated according to Equations (1) and (2). The evaporative resistance ReT was measured using a non-standard method based on the measurement of moisture loss from the "artificial skin" covering the entire surface of the manikin [27] and recalculated from the measured heat loss according to Equation (3) [27].…”

“…Based on the measured values of I T and R eT , the static clothing permeability index i m was calculated according to Equation (4) described in the standard EN ISO 9920 [28] for all measured types of protective ensembles. In the recalculation of the i m value, however, it is necessary to take into account a certain uncertainty in the measurement [27,29].…”

A Database of Static Thermal Insulation and Evaporative Resistance Values of Dutch Firefighter Clothing Items and Ensembles

“…At the same time, when modern office and casual clothing are measured in a systematic way, data on industrial workwear are not as easily available. Some exceptions are studies on military [ 64 , 65 , 66 , 67 , 68 , 69 ], ambulance [ 70 , 71 ], cold protective [ 72 , 73 , 74 , 75 , 76 , 77 ], and some agricultural [ 78 , 79 ] clothing systems. Although, the studied clothing systems cover a wide variety of clothing configurations, it may be suspected that specialized clothing, e.g., the ones used by firefighters, may behave differently due to the protective layers and their combinations.…”