The Montreal Heart Institute-led research has shed light on the impact of electric fan use on older adults during extreme heat exposures. The study found that using a fan at 38 °C and 60% relative humidity led to a modest decrease in core temperature and increased comfort levels. However, using a fan at 45 °C and 15% relative humidity actually raised core temperature and caused discomfort.
The CDC advises against using fans above 32 °C due to concerns that increased airflow could accelerate heat gain in vulnerable populations. While previous studies have suggested that airflow may be beneficial in high humidity conditions, the effects of fan use in very high temperatures on older adults have been unclear. With older individuals being at a higher risk of heat-related health issues, finding practical and affordable cooling solutions is crucial.
The research, published in JAMA Network Open, involved a secondary analysis of a randomized crossover clinical trial. The study included 58 elderly participants, with and without coronary artery disease, who underwent heat exposures in a climate chamber set at either 38 °C and 60% humidity or 45 °C and 15% humidity.
During the humid trial, fan use was found to lower core temperature, increase sweat rate, and improve thermal sensation and comfort levels. Skin wetting also had a positive impact on thermal perception. Combining fan use and skin wetting produced the best results in terms of comfort and thermal sensation.
In contrast, in the dry chamber, fan use actually raised core temperature, increased sweating, and worsened comfort levels. Skin wetting alone improved thermal sensation but did not affect comfort.
The researchers concluded that electric fans can be a safe and cost-effective cooling option for older adults during hot, humid weather at 38 °C. However, they should be avoided in very hot, dry conditions. Simple skin wetting can help manage heat stress and improve comfort without impacting core temperature.
These findings can be used by public health agencies to refine heat safety messages for seniors and provide them with practical strategies to stay cool during extreme heat events. By understanding the impact of fan use and skin wetting on older adults, we can better protect vulnerable populations from the risks of heat-related illnesses.
This article was written by Justin Jackson, edited by Sadie Harley, and fact-checked by Robert Egan. It is a result of meticulous human effort and relies on reader support to sustain independent science journalism. If you value this reporting, consider making a donation to support our work and receive an ad-free account as a thank you. For more information, refer to the original study published in JAMA Network Open. Thank you for supporting independent science journalism in 2025.
