The protection of personnel against high air and radiant temperatures is a problem that has been confronting industry for many years now, and for many industrial situations it still has not been solved. The experiments reported here were intended to determine the most suitable form of insulation for a hot entry suit for use primarily in furnace wrecking where mean radiant temperatures of 200°C. are met and where heat-reflecting garments are unsuitable due to the rapid deterioration of the reflecting surface.From a preliminary consideration of the problem it was concluded that a ventilated garment was required and that conventional ventilated garments in which air is induced to flow parallel to the body surfaces (axial ventilation) are basically unsound in design as the air is not utilized for the transfer of heat in the most efficient manner. A new form of ventilation was therefore developed in which air flows out through a permeable suit (radial ventilation). This form of ventilation produces what is called dynamic insulation, and this method of insulation, when compared with two alternative methods on a physical model, was found to be very effective.The model experiments were confirmed by comparative trials of three ventilated suits each using one of three different forms of insulation thought to be suitable for use in heat-protective clothing.Physiological measurements made on the subjects and physical measurement made on the suits confirmed that dynamic insulation is the most suitable insulation for a hot entry suit for furnace wrecking.With the air flows used in these experiments, dynamic insulation had a thermal conductance one-fifth that of conventional static insulation, and sweat losses and oral temperature rises were reduced by one-third and one-half respectively.
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