Electric fan use for cooling during hot weather: a biophysical modelling study

Nathan B Morris; Georgia K Chaseling; Timothy English; Fabian Gruss; Mohammad Fauzan Bin Maideen; Anthony Capon; Ollie Jay

doi:10.1016/S2542-5196(21)00136-4

Electric fan use for cooling during hot weather: a biophysical modelling study

Lancet Planet Health. 2021 Jun;5(6):e368-e377. doi: 10.1016/S2542-5196(21)00136-4.

Authors

Nathan B Morris¹, Georgia K Chaseling², Timothy English³, Fabian Gruss⁴, Mohammad Fauzan Bin Maideen⁴, Anthony Capon⁵, Ollie Jay⁶

Affiliations

¹ Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.
² Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Department of Pharmacology and Physiology, University of Montreal, Montreal, QC, Canada.
³ Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Faculty of Medicine and Health, and Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia.
⁴ Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia.
⁵ Sydney School of Public Health, The University of Sydney, Sydney, NSW, Australia; Monash Sustainable Development Institute, Monash University, Melbourne, VIC, Australia.
⁶ Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Sydney School of Public Health, The University of Sydney, Sydney, NSW, Australia; Faculty of Medicine and Health, and Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia. Electronic address: ollie.jay@sydney.edu.au.

PMID: 34119011
DOI: 10.1016/S2542-5196(21)00136-4

Abstract

Background: In hot weather, electric fans can potentially provide effective cooling for people, with lower greenhouse gas emissions and cost than air conditioning. However, international public health organisations regularly discourage fan use in temperatures higher than 35°C, despite little evidence. We aimed to determine humidity-dependent temperature thresholds at which electric fans would become detrimental in different age groups.

Methods: We used biophysical modelling to determine the upper humidity-dependent temperature thresholds at which fan use would become detrimental (ie, worsen heat stress) for healthy young adults (aged 18-40 years), healthy older adults (aged ≥65 years), and older adults taking anticholinergic medication. We also obtained hourly environmental data for the period Jan 1, 2007, to Dec 31, 2019, for 108 populous cities to determine the number of days fan use would be effective for cooling, standardised to a 31-day hot weather month. We established simplified temperature thresholds for future fan use recommendations on the basis of temperatures below which fan use would never have been detrimental between Jan 1, 2007, and Dec 31, 2019, across all prevailing levels of ambient humidity.

Findings: According to our model, fan use would have been beneficial on 30·0 (96·6%) of 31 hot weather days for healthy young adults and 29·4 (94·9%) of 31 hot weather days for both older adults and older adults taking anticholinergic medication between Jan 1, 2007, and Dec 31, 2019. Adherence to the current WHO recommendation of fan use below temperatures of 35°C only, fan use would have been recommended on 27·2 days (87·7%) of 31 hot weather days. According to our simplified thresholds for fan use (at temperatures <39·0°C for healthy young adults, <38·0°C for healthy older adults, and <37·0°C for older adults taking anticholinergic medication), fan use would have been recommended on 29·6 (95·5%) of 31 hot weather days in healthy young adults, 29·4 (94·8%) days in healthy older adults, and 28·8 (93·0%) days in older adults taking anticholinergic medication between Jan 1, 2007, and Dec 31, 2019.

Interpretation: Electric fan use, particularly for healthy young adults, would not have worsened heat stress on the majority of study days between 2007 and 2019. Our newly proposed thresholds for fan use provide simple guidelines that improve future heatwave fan use recommendations.

Funding: None.

MeSH terms

Aged
Body Temperature Regulation*
Cold Temperature
Heat Stress Disorders*
Hot Temperature
Humans
Humidity
Young Adult