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Measuring wet bulb globe temperatures at point-of-exertion in worldwide UK military settings: a longitudinal observational study determining the accuracy of a portable WBGT monitor
  1. Patricia Falconer Hall1,
  2. J Blackadder-Coward2 and
  3. H Pynn3
  1. 1AMS Support Unit, Army Medical Services, Camberley, UK
  2. 2Academic Department of Military General Practice, Royal Centre for Defence Medicine, Birmingham, UK
  3. 3Research and Clinical Innovation, Royal Centre for Defence Medicine, Birmingham, UK
  1. Correspondence to Patricia Falconer Hall, AMS Support Unit, Army Medical Services, Camberley GU15 4PQ, UK; patricia.falconerhall{at}


Introduction Heat illness among the UK Armed Forces is usually exertional, and therefore preventable, yet the incidence has not reduced since 2011. JSP 539 explicitly states that wet bulb globe temperature (WBGT) should be measured ‘at the location of greatest heat risk’, not ‘that of most convenience’. A handheld WBGT tracker used at point-of-exertion could reduce this incidence if proven to be as accurate as the current in-service device.

Methods Longitudinal observational comparison and equipment feasibility study of the Kestrel 5400 and QUESTemp 34 (QT-34) in worldwide firm base and deployed UK Armed Forces locations. The locations chosen were Kenya, South Sudan, Belize, Tidworth, Aldershot and Brecon. Paired data points of WBGT readings were collected from November 2017 to August 2018 in all weather conditions.

Results WBGT readings were comparable between the QT-34 and Kestrel 5400 across the UK and overseas. In addition, there was no change in accuracy between readings taken from the Kestrel 5400 when tripod-mounted and handheld. The Kestrel was easy to set up and far less susceptible to resupply or power supply limitations, as it requires no user input for wet bulb temperature, and runs on AA batteries.

Conclusion This equipment feasibility study has shown that the Kestrel 5400 gives an acceptable accuracy and is easier to use than the QT-34. The authors recommend that the Kestrel 5400 is introduced as an adjunct to the QT-34, and its use within the military setting monitored through ongoing comparative data collection in a large-scale proof-of-concept study.

  • occupational & industrial medicine
  • risk management
  • health policy

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  • Collaborators Jason Smith; Aidan Hanrath.

  • Contributors PFH, Emergency Medicine ST2, Army Medical Services, Camberley, UK. JB-W, Lecturer General Practice, Academic Department of Military General Practice, Research and Clinical Innovation, Edgbaston, Birmingham. HP, Defence Consultant Advisor in Pre-Hospital Emergency Care, Research and Clinical Innovation, Edgbaston, Birmingham. PFH wrote the initial draft of the paper, with revisions and additions made by JB-C and HP.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Disclaimer The opinions expressed here are those of the authors and do not necessarily represent the views of the UK Defence Medical Services. Study approval not needed. This paper did not involve human subjects or any patient information. It involved the authors taking contemporaneous paired measurements from each WBGT device and analysing the data.

  • Competing interests The Kestrel devices were donated on loan to DCA PHEC by Fenton Pharmaceuticals for the purposes of this study and returned at the end of the data collection.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request.