Older adults should avoid electric fans during extremely hot and dry weather because they can triple strain on the heart, Australian researchers say.

Older adults should instead wet their skin to stay cool, according to the researchers from the University of Sydney and Canada’s Montreal Heart Institute.

However, they said fans were safe and effective in hot and humid weather.

The research team, which included geriatricians and physiologists, exposed elderly volunteers to extreme hot and dry conditions (45°C and 15% humidity) or hot and humid conditions (38°C and 60% humidity) for three hours at a time before measuring changes in their heart rate and blood pressure.