An electric fan running in a perfectly insulated and hermetically . sealed room would not make the air in the room cooler, as commonly supposed. In fact, because of the friction developed in the fan, the temperature of a room is slightly increased instead of decreased by setting the air in rapid motion. The cooling effect of the fan results from the fact that the temperature of the air is lower than the temperature of a person’s skin and each puff of air absorbs heat and moisture as it passes. Wind blowing on a thermometer does not affect the reading of the instrument unless the wind is warmer than the air surrounding the thermometer. If a person blows on a thermometer it will register greater heat because a person’s breath is generally warmer than the surrounding air. But as a rule an electric “fan running in front of a thermometer has little effect on the reading because the temperature of the moving air and the rest of the air are virtually the same.
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