A practical heat stress assessment methodology for UK industry

HSE Press Release E196:02 - 21 October 2002

The Health and Safety Executive (HSE) has published research into developing a method for assessing stress caused by exposure to heat in the in the workplace. The research concludes that large parts of UK industry have difficulty in managing and assessing heat stress. It has long been known that work related heat stress could compromise health and safety and lead directly or indirectly to worker injury and death.

As a result the HSE sponsored a research project to ensure that developments in heat stress assessment were evaluated and documented in a valid and usable methodology.

The work was undertaken by Prof. Ken Parsons and Damien Bethea at the Human Thermal Environments Laboratory at Loughborough University who has been involved in heat stress research for over 20 years. The researchers were asked to develop a practical means of assessing heat stress in industrial operations. Damien Bethea is now employed by the Health and Safety Laboratory (HSL) in Sheffield where he works on thermal stress and comfort.

Their study confirmed that problems with the presentation and content meant that current documents might not be used as intended. The researchers then consulted other recognised experts and practitioners to guide them in developing a new approach to heat risk assessment. This enabled them to derive a checklist risk assessment method.

The practical heat stress assessment method was successfully piloted in UK industries such as steel mills where heat stress has posed a problem. The health and safety personnel who participated in these trials contributed to the development of the method by identifying areas where it needed modification this in turn lead to a new method, which was effective at identifying risk factors for heat stress.

Welcoming the report Dr Ron McCaig, Head of the Human Factors Unit, said

"The complexity of some methods of heat stress assessment may deter employers from taking effective action to control these risks. This new risk assessment method has the potential to help identify the risk factors contributing to the risk of heat stress at work. This will allow employers to control these risks taking further advice if necessary."

HSE is now considering how to apply this approach to heat stress risk assessment more widely, possibly in the form of leaflets and guidance.

Notes to editors

1. Criticisms of existing methods for the assessment of heat stress are mainly in three areas:

• The SCOPE of the methods is often not sufficient to meet the varied realities of industrial heat stress. For example, methods do not account for the effects of protective clothing and equipment, yet workers in hot environments often wear this sort of clothing;
• The VALIDITY of methods has been questioned. Does the method really relate to the heat strain on the workers?
• In recent years the USABILITY of methods has been recognised as important. Methods may be valid and sufficient in scope but if they are too complex or not presented in a way that is complementary to the context, people and organisations who use them then they may not be used correctly, if at all.

2. The project presented in this report is unique in that it addresses the issues of both validity and usability. It was conducted in parallel with a number of national and international initiatives into heat stress assessment. The present project achieved its aim of investigating the validity and usability of existing (ISO 7933; 1989) and proposed (predictive heat strain and risk assessment strategy) methods (by the European funded BIOMED II project).

3. Such methods are considered unnecessarily scientific and may not encourage their use. The format and the information provided do not satisfy ergonomic guidelines of usability. The need for a more practical heat stress assessment methodology was identified. A framework was formulated for the design, development and evaluation of such a methodology. This framework consisted of three stages; an Exploratory Stage, a Design and Development Stage and an Evaluation Stage. This resulted in the development of a practical heat stress assessment methodology.

4. A model report was developed on how to assess heat stress in the workplace; this was piloted in industry (e.g. Steel Mills) to see if they could follow the technical guidelines detailed in the report. This was successful as the industries piloted were able to follow the method described in the report to assess heat stress and suggest additional modifications to the method.

5. The HSE, with HSL are now developing general guidance on heat stress risk based on the findings of this research. This will provide guidance on the management, assessment and control of heat stress.

The user centred approach used in this study has shown input from users is beneficial to the development of HSE guidance.

The development of a practical heat stress assessment methodology for use in UK industry RR 008 is available on HSE website at http://www.hse.gov.uk/research/

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