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Fans beneficial in heat wave conditions: Study


Contrary to general public health guidance warning against fan use during heat wave conditions, fans may actually be helpful in keeping one’s body cool, a new study suggests.

The study demonstrated that electric fans prevent heat-related elevations in heart rate and core body temperature.

Researchers examined the effect of fan use at temperatures and humidities that can no longer be physiologically tolerated without rapid increases in heart rate and core body temperature.

They found that electric fans prevented heat-related elevations in heart and core temperature up to approximately 80 percent relative humidity at 36 degrees Celcius and 50 percent relative humidity at 42 degrees Celcius.

"Thus, contrary to existing guidance, fans may be effective cooling devices for those without air conditioning during hot and humid periods," said study author Ollie Jay of the University of Sydney, Australia.

Sweat evaporation declines with increasing humidity, so in more humid environments fans may not prevent heat-induced elevations in cardiovascular and thermal (core temperature) strain.

Wearing shorts and t-shirts, eight healthy males (average age, 23 years) sat in a chamber maintained at temperatures equal to (36 degrees Celcius) or exceeding (42 degrees Celcius), the limits currently recommended for fan use. 

Each temperature was tested with and without an 18-inch fan facing the participant (from about 3 feet).

After a 20-minute baseline period, relative humidity was increased in 15 equal steps from 25 percent to 95 percent at 36 degrees Celcius and from 20 percent to 70 percent at 42 degrees Celcius.

The heart rate and core temperature of the study participants were measured throughout.

"Advice to the public to stop using fans during heat waves may need to be re-evaluated," Jay added.

The study was published in JAMA: Journal of the American Medical Association.