Ceiling fan be used to reduce the stratification of warm air in a room by forcing it down to affect both occupants' sensations and thermostat readings, thereby improving climate control energy efficiency. Punkah-type ceiling fans date back to 500 BC, and are native to India. Unlike modern rotary fans, these punkah fans move air by moving to and fro, and were operated manually by cord. The first rotary ceiling fans appeared in the early 1860s and 1870s in the United States. At that time, they were not powered by any form of electric motor. Instead, a stream of running water was used,
Ceiling fan throughout the United States prohibit residential ceiling fans from being mounted with the blades closer than seven feet from the floor; this sometimes proves, however, to not be high enough. If a ceiling fan is turned on and a person fully extends his or her arms into the air, as sometimes happens during normal tasks such as stretching or changing bedsheets, it is possible for the blades to strike their hands, potentially causing injury. Also, if one is carrying a long and awkward object, one end may inadvertently enter the path of rotation of a ceiling fan's blades, which can