Time of testing Insulation

A single sleeping assembly for general issue in the British Army was designed by the Stores and Clothing Research and Development Establishment (SCRDE) to replace the in-service, down and feather General Service and Arctic sleeping bags. This new sleeping assembly consists of a synthetic, hollow, staple-fibre fIlled sleeping bag; a waterproof "bivvy " bag; a compression sack and a sleeping mat (Davies, 1987). The British Army required a sleeping bag which permitted 4 hours rest at-35°C and 8 hours at-20°C. It was therefore necessary to investigate the effects of use in the field and of laundering on the synthetic filling of the sleeping bags using both physical and physiological methods. METHODS AND RESULTS A sample of sleeping bags was weighed and the (uncompressed) thermal insulation value was assessed using a non-destructive method in which a complete sleeping bag is placed over a heated plate and a steady-state temperature gradient established and measured (Watson-Hopkinson, 1990). Mter this initial measurement the bags were issued to selected Army units for use during operational training. These same sleeping bags were recalled after 4 and 12 month's use to be re-weighed and to have their thermal insulation value re-measured. The effects of this field use are shown in Table 1. Table I. Insulation aTUi weights 0/46 sleeping bag