title: Should electric fans be used during a heat wave?
abstract: Heat waves continue to claim lives, with the elderly and poor at greatest risk. A simple and cost-effective intervention is an electric fan, but public health agencies warn against their use despite no evidence refuting their efficacy in heat waves. A conceptual human heat balance model can be used to estimate the evaporative requirement for heat balance, the potential for evaporative heat loss from the skin, and the predicted sweat rate, with and without an electrical fan during heat wave conditions. Using criteria defined by the literature, it is clear that fans increase the predicted critical environmental limits for both the physiological compensation of endogenous/exogenous heat, and the onset of cardiovascular strain by an air temperature of ∼3-4 °C, irrespective of relative humidity (RH) for the young and elderly. Even above these critical limits, fans would apparently still provide marginal benefits at air temperatures as high as 51.1 °C at 10%RH for young adults and 48.1 °C at 10%RH for the elderly. Previous concerns that dehydration would be exacerbated with fan use do not seem likely, except under very hot (>40 °C) and dry (<10%RH) conditions, when predicted sweat losses are only greater with fans by a minor amount (∼20-30 mL/h). Relative to the peak outdoor environmental conditions reported during ten of the most severe heat waves in recent history, fan use would be advisable in all of these situations, even when reducing the predicted maximum sweat output for the elderly. The protective benefit of fans appears to be underestimated by current guidelines.
authors.affiliation: Thermal Ergonomics Laboratory, Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, 75 East Street, Lidcombe, NSW 2141, Australia; School of Human Kinetics, University of Ottawa, K1N 6N5, Canada. Electronic address: ollie.jay@sydney.edu.au.
authors.forename: Ollie
authors.initials: O
authors.lastname: Jay
authors.affiliation: School of Human Kinetics, University of Ottawa, K1N 6N5, Canada.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Cramer
authors.affiliation: School of Human Kinetics, University of Ottawa, K1N 6N5, Canada.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Ravanelli
authors.affiliation: Environmental Ergonomics Research Centre, Loughborough University, Leics LE11 3TU, United Kingdom.
authors.forename: Simon G
authors.initials: SG
authors.lastname: Hodder
mesh_terms: D001833:Body Temperature Regulation / Q000502:physiology*; D055615:Electrical Equipment and Supplies; D055874:Extreme Heat / Q000009:adverse effects*; D018882:Heat Stress Disorders / Q000517:prevention & control*; D006794:Household Articles / Q000295:instrumentation*; D006801:Humans; D008962:Models, Theoretical; D011634:Public Health; D012881:Skin Temperature; D013312:Stress, Physiological; D013546:Sweating / Q000502:physiology; D014691:Ventilation / Q000295:instrumentation*
keywords: Air flow; Extreme heat events; Hydration