Editor—In his editorial Keatinge referred to fans as a prevention for heat injury.1 However, in severe heat, fans can add to the level of heat stress.
Writing about the fatal heat wave of 1995 in Chicago, the US Centers for Disease Control and Prevention noted that fans should not be used for preventing heat related illness in areas with high humidity because increased air movement (such as from fans) is associated with heat stress when the ambient temperature exceeds approximately 100°F (37.8°C) and because fans are not protective at temperatures greater than 90°F (greater than 32.3°C) with humidity greater than 35% (the exact temperature varies with the humidity).2
Fans can be extremely effective when combined with the use of a fine water mist in areas of normal or low humidity, but if the temperature and humidity are high, even water mist plus fanning is not reliable for cooling. In such cases people at risk of heat injury are advised to take a cool shower or bath, or seek shelter in an air-conditioned building.
Competing interests: None declared.
References
- 1.Keatinge WR. Death in heat waves. BMJ 2003;327: 512-3. (6 September.) [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Centers for Disease Control and Prevention. Heat-related mortality—Chicago, July 1995. MMWR Morb Mortal Wkly Rep 1995;44; 577-9. [PubMed] [Google Scholar]