The effect of vapor permeable versus non-vapor permeable shirts on heat stress

Abstract

Everything in a paper mill operates on a gargantuan scale, including the hazards, which can include everything from falls to in-running nip points to heat stress. While heat stress would not be considered one of the major hazards, it can still put some employees at a high risk of developing heat stress-related injuries. To combat the threat posed by heat stress, a variety of different engineering and administrative controls such as work restrictions, ventilation changes and vapor permeable clothing have been developed. Two separate tests were conducted to study the effects of clothing and ventilation controls on worker heat strain. In the first test, five subjects wore a shirt containing vapor permeable material followed by a cotton shirt while conducting normal work duties. The vapor permeable material was manufactured by Nike, Inc. and marketed under the trade name Dri-FIT. A Questemp II personal heat stress monitor was used to determine body core temperatures and a subjective evaluation of the two shirts was conducted. Results indicate the vapor permeable shirt reduced core temperatures by about 0.3-0.5ºC compared to the cotton shirt. In addition, the vapor permeable shirt was rated to be more comfortable and to have a faster drying time than the cotton shirt. The data suggests that vapor permeable shirts allow more skin cooling to take place, thereby reducing the body core temperature. In the ventilation test, environmental heat stress readings were taken with a Metrosonics hs-360 heat stress monitor and were used to determine if increasing building make-up air and adding a new exhaust fan would reduce temperatures in the pulp and paper production areas. Results indicated a 1-1.5ºC temperature reduction in the pulp production area and about a 5ºC temperature reduction in the paper production area. The data suggests increasing make-up air and adding an exhaust fan can decrease temperatures in the pulp and paper production area, however, temperatures outside the mill dropped by about 5-8ºC between ventilation changes, which may have had an effect on the temperature inside the mill. It was concluded that using vapor permeable clothing and modifying the building’s ventilation by increasing make-up air and adding an exhaust fan could reduce heat stress and worker heat strain. Recommendations were made for the mill to suggest the vapor permeable shirt as a heat stress control for affected employees and to install additional exhaust fans and increase make-up air in areas where the tested ventilation modifications had no effect.