PUBLIC health guidelines that recommend turning off fans when temperatures exceed 35 degrees are likely flawed and may unnecessarily expose vulnerable people to health effects during heatwaves, researchers at the University of Sydney say.
Ollie Jay, director of the university's Thermal Ergonomics Laboratory that simulates a range of heat extremes and how humans respond, said advice in many jurisdictions for coping with heatwaves was "not really based on a lot of scientific evidence".
By adjusting the laboratory's special heat room – originally set up three decades ago by the late Professor Martin Thompson to help athletes on hot days – the researchers have been able to study how people handle precise heatwave conditions.
These include mimicking a 2009 Adelaide heatwave when the mercury climbed to 48 degrees with humidity of just 5-6 per cent, and a 2015 "heat dome" over the Pakistani city of Karachi when residents endured 45 degrees at about 50 per cent humidity.
The aim is to develop strategies for the public to cope, such as with or without a fan and applying water, for a range of ages and medical conditions.
Planetary health
The work comes as a heatwave continues to bake eastern Australia, with much of Sydney expected to exceed 40 degrees on Thursday. Adelaide and Melbourne both clocked mid to high-30s on Wednesday.
Sydney University will also launch its new Planetary Health Platform on Thursday aimed at bringing together disciplines – from public health and religion, to architecture and economics – to build knowledge and capacity for societies to cope with intensifying threats such as from climate change.
Research challenging advice on electric fan use during heatwaves was raised in earlier papers by Associate Professor Jay and other scientists, such as in 2014.
They noted authorities often relied on data showing that increased air movement above about 35 degrees added to skin temperature from convection.
However, as people tend to perspire, fans help to accelerate evaporation of sweat, providing cooling.
"Young, healthy people who are able to sweat quite freely experience less strain at 42 degrees with a fan than at 36 degrees without a fan," Professor Jay said. "The benefits in terms of extra sweat that evaporates far outweighs the extra heat that is loaded on the body [from convection>[/embedp>