A scientist has issued a warning about using fans during the UK's recent 35°C heatwave, as millions seek relief from the record-breaking temperatures. A new study by the University of Ottawa reveals that electric fans may not provide effective cooling during extreme heat, contrary to popular belief.
How Fans Actually Work
According to Science How Stuff Works, fans do not lower a room's overall temperature. Instead, they move air around, which can slightly increase the room's heat due to the motor's operation. However, the moving air facilitates sweat evaporation, making individuals feel cooler even though the ambient temperature remains unchanged or rises slightly.
In high humidity environments, the effectiveness of fans is reduced because the air is already saturated with moisture, limiting sweat evaporation. This makes fans less effective in humid conditions compared to drier environments where evaporation occurs more readily.
University of Ottawa Study Findings
Research led by post-doctoral fellow Robert Meade at the Human and Environmental Physiology Research Unit, overseen by Dr. Glen Kenny, a professor of physiology, examined the cooling benefits of fans during extreme temperatures. The study used human heat balance modelling techniques developed in 2015 to calculate core temperature across various conditions and assumptions.
Professor Meade stated: "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). 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."
Recommendations for Vulnerable Groups
The study, reported in Science Daily, urges health organisations to continue cautioning against depending on fans during extreme heat events, particularly for elderly people and other vulnerable groups at greater risk of heat stroke and other serious health complications. Instead, the focus should be on ensuring access to alternative cooling methods, such as air conditioning, while exploring ways to make these solutions more accessible and environmentally sustainable.
Results from 116,640 alternative models in sensitivity analyses indicated that fans likely do not significantly reduce core temperature in high heat or match the cooling of air conditioning. Comparisons with more advanced modelling techniques and laboratory heat wave simulations supported this conclusion.
