When the weather gets hot, the first thing many of us do is switch on a fan. However, scientists have now debunked their usefulness in extremely hot temperatures.
Severe heatwaves are becoming more common because of global warming, meaning ways to keep cool are getting more important.
New research, led by post-doctoral fellow Robert Meade at the Human and Environmental Physiology Research Unit at the University of Ottawa, used human heat balance modeling to test the effectiveness of fans.
In a range of scenarios it was found that they do not "significantly reduce core temperature in high heat." They also do not match the cooling provided by air conditioning, Meade said in a statement. Further comparisons with more advanced modeling amid heat wave simulations also supported this find.
"Fans do improve sweat evaporation, but this effect is not strong enough to significantly lower your body's internal temperature when it's already really hot (above 33-35 C)," Meade said in a statement. "In older adults, who may have a reduced ability to sweat, fans provide even less cooling benefits. In fact, even in younger adults, fans only provide a small fraction of the cooling power of air conditioning."
So, fans can be good at cooling in moderate temperatures but it is a different story for extreme heat.
Health agencies worldwide have historically cautioned that electric fans accelerate body-heat gain during extremely hot weather. However, guidance published since 2021 has suggested that fans can still cool the body in air temperatures up to 40 C by facilitating sweat evaporation. However, the latest research, published in the journal Lancet Planetary Health, suggests health agencies should continue telling people to avoid using fans when air temperatures are higher than 35 C. This is especially true of individuals with compromised sweating capacity, such as adults aged 65 years or older. Improving access to other cooling methods, such as air conditioning or evaporative coolers, is recommended.
"Keeping indoor temperature cool is important for vulnerable individuals, but cooling strategies like air conditioning can be costly and harmful to the environment. It is crucial that we improve the accessibility and sustainability of air conditioning and other forms of ambient cooling to protect those in need," Meade said in the statement. "Fans can still have an important role in this, since they can be effective for cooling at lower temperatures, meaning we don't have to set our air conditioners so low. However, when it gets really hot, a fan alone is not going to cut it."
Previous research has shown that as climate change worsens, extreme heatwaves are set to become more commonplace. This means people will have to adapt to the changing temperatures.
Earlier this year, data from the World Meteorological Organization showed that last year was the hottest year on record.
The data showed that the average global temperature in 2023 was 1.46 C (2.6 F) higher than the pre-industrial level.
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about extreme heat? Let us know via science@newsweek.com.
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
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Robyn White is a Newsweek Nature Reporter based in London, UK. Her focus is reporting on wildlife, science and the ... Read more
