Electric fans are NOT safe for cooling down when the heat is dry: Study warns they may raise your body temperature, heart rate and blood pressure if it’s not humid
- Participants were observed under two types of heat waves: one that was very hot and dry, and one that was cooler but more humid
- With the hot and dry condition, electric fans raised core body temperature, heart rate and blood pressure
- But when used in the hot but humid condition, the fans did just the opposite
- Researchers say the findings are in contrast with recommendations from the CDC and WHO that warn against using fans in extreme heat
Electric fans are not safe for cooling down when temperatures are high and humidity is low, a new study says.
Researchers found that when the heat index – which measures air temperature and humidity – is relatively low, fans raised core temperature, heart rate and blood pressure.
But when temperatures were high as was humidity, the fans lowered all three measures.
Currently, several health agencies – including the World Health Organization and the Centers for Disease Control and Prevention – recommend not using electric fans in extreme heat because fans increase the work the body does to cool down.
The team, from the University of Sydney in Australia, says these recommendations are not based on any scientific evidence and that its findings could help prevent people suffering from dehydration or heat stroke during sweltering heatwaves.
A new study from the University of Sydney found that electric fans used when temperatures and humidity were high helped lower body temperature, hear rate and blood pressure (file image)
For the study, published in the Annals of Internal Medicine, the team recruited 12 male participants.
They were monitored for two hours in conditions mimicking two types of heat waves: one that was very hot and dry like the California heatwave in July 2018, and one that was cooler but more humid like the Chicago heatwave in July 1995.
Participants were tested for thermal strain (rectal temperature), cardiovascular strain (heart rate and blood pressure) and risk of dehydration (whole-body sweat rate).
The team found in hot and humid condition, with a heat index of about 133F, fans helped lower core body temperatures, heart rate and blood pressure.
But in very hot and dry conditions, even with a heat index of about 115, fans raised all three measures.
Currently, the World Health Organization and the Centers of Disease Control and Prevention suggest fans are not beneficial when the temperature rises above 95F.
Senior author Dr Ollie Jay, an associate professor of thermoregulatory physiology at the University of Sydney, says the team’s findings show just the opposite and that the recent heatwaves in Europe and the US make it urgent for advice to be issued to protect people against heat-related illness.
In Europe, a heatwave this summer shattered several record temperatures across the western half of the continent.
Areas of Belgium and the Netherlands hit temperatures above 104F during the last week of July, according to Ars Technica.
The UK had temperatures reach highs of about 102F while Germany and Paris, France, saw the mercury climb to at least 108F.
Meanwhile, in the US, new one-day temperature records were recorded in at least six places on July 20 including John F Kennedy International Airport in New York and Detroit Metropolitan Airport.
‘Our results suggest that under environmental conditions that represent the vast majority of peak heatwaves in the United States and Europe fans should be recommended and the guidelines issued by most public health authorities are unnecessarily conservative,’ said Dr Jay.
‘It is only when the air temperature is very high and humidity is very low that fans are detrimental, which can be seen in arid conditions such as Phoenix or Las Vegas in the US, or Adelaide in South Australia.’
For future research, the team plans on looking at the effectiveness of different methods of cooling that can be easily executed by the elderly during a heatwave.