Hand cooling, protection and performance in cold environments

Sammanfattning: This dissertation presents experimental data on hand/finger cooling responses and performance in cold environments with and without gloves. The first part concerned studies of hand/finger cooling behaviors under various cold conditions. The experimental results with human subjects indicate that a reduction in the contact temperature is a function of thermal properties and surface temperature of the materials, skin and the nature of the contact as well. Manual performance reduced after gripping the cold objects. A decrease of the hand skin temperature causes the performance loss. The safety criteria for the contact temperature are suggested to be 0°C (freezing), 7°C (numbness) and 15°C (pain sensation). An artificial heated finger model was developed and used to derive additional cooling information for extremely cold metallic surfaces. All results were utilized to establish relations between contact temperature, contact time and material used and compiled in an ergonomic database. The information can be used for risk assessment and for setting temperature limit values for products in appropriate standards for cold work. Manual performance, such as dexterity and tactile sensitivity of gloved hand in the cold operation, has been investigated. The relations among physical properties of protective gloves and hand performance were evaluated objectively and subjectively. Human subjects wearing four different work gloves and three different types of gloving (outer, inner and double) participated in the experimental studies during cold exposure. It is indicated that wearing various work gloves gives impairment in both manual dexterity and tactile sensitivity in cold operations. The performance was affected both by glove design and by hand/finger cooling. Use of double gloving is recommended to be an appropriate approach to use the protective gloves in the cold while inner glove can be used to perform some precision work. In extremely cold exposures hand cooling overrides the effect of glove on tactile performance. Development and use of an electrically heated glove should be considered for hand protection in a prolonged cold operation.