The Cooling Budget of a Fevered Adult: How Much Heat Water, Air, and Fanning Can Remove, and What One Degree Costs

This simulated study calculates how much heat can be removed from a resting adult weighing 70 kg during fever, and what lowering the core temperature by one degree requires. The body stores 242.9 kJ per degree, and metabolic production at the reference fever of 39.5 °C is 112.8 W. Bare skin in still air in a room at 30 °C and 50 percent relative humidity removes 335.8 W after metabolic production is subtracted, which would lower the temperature by one degree in 12.1 minutes if the rate held constant. Wetting the whole skin surface and fanning it in the same room raises the net rate to 1400.8 W and shortens the time to 2.9 minutes, with about 0.1 litres of water evaporated per degree. Humidity weakens evaporation but does not stop it in these cases, because the skin is warmer than the air: at 35 °C in still air the ceiling at which evaporation and dry loss together only just match metabolic production is 90.4 percent relative humidity, while the corresponding fanned values exceed the physically possible range. These are upper-bound calculations from stated assumptions, not measurements, and they do not describe a treatment.