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Moving air around isn’t the same as cooling it off.
Many people rely on electric fans to help them beat the heat, but there are certain conditions when the electric fan is useless. The World Health Organization has been advising people not to rely on electric fans when the temperature exceeds 95 degrees while the US Environmental Protection Agency suggests not to use them over 99 degrees.
Researchers became curious about the science behind this reasoning and decided to test it out. In a small study, they found the evidence to be too clean cut with some loopholes. Environments that were very hot and humid benefited people more than when the environments were dry and hot.
They used a heat index, which is a combination of air temperature and humidity, to set up the expectations for what temperature feels like to humans. Electric fans still proved to be effective at reducing the core body temperature of people with a heat index up to 133 degrees. The heat index was cut down to 115 degrees when the heat was dry.
Fans are not detrimental to people when humidity is high, but can be detrimental when humidity is low. You would expect to find these kinds of conditions in Phoenix or Las Vegas. These results are positive for people who cannot afford air conditioning in their homes. The fans, for the most part, are not increasing the heat that people are experiencing and they are still a good alternative to just opening up the windows.
