Currently there is no statutory legal upper limit for temperatures in the workplace, mainly due to the fact that legislators have not yet made provision for heat waves of the nature we have experienced over the last few years.

Control of the risk to the health of workers from heat stress (arising from working in high air temperatures, exposure to high thermal radiation or high levels of humidity) is based on the legal duty placed on employers to carry out a risk assessment, taking a number of pertinent factors into consideration These include:

• Measures to control the workplace environment, in particular heat from any source. Minimising the risk of heat stress may mean using local cooling by increasing ventilation rates and maintaining the appropriate level of humidity;
• Restriction of exposure by, for example, re-organising tasks to build in rest periods or other breaks from work. This will allow workers to rest in an area where the environment is comfortable and, if necessary, to replace bodily fluids to combat dehydration. If work rates cause sweating, workers may need frequent rest pauses for changing into dry clothing;
• Medical pre-selection of employees to ensure that they are fit to work in hot environments;
• Use of suitable clothing, which may need to be heat resistant;
• Acclimatisation of workers to the environment in which they work;
• Training in the precautions to be taken;
• Supervision, to ensure that the precautions identified by the assessment are taken; and
• Minimising the effects of sources of radiant heat, when working in environments where work equipment generates heat e.g. coal furnaces, engineering plant etc., by perhaps providing appropriate insulation.

Further guidance on the issue of heat stress in the workplace, is available from the |Health & Safety Executive (HSE) website in particular thermal comfort, as it looks more closely at employers' legal obligations.

Further information:

• |Workplace Temperature and Thermal Comfort - Health & Safety Executive
• |Managers Guide to Thermal Comfort in the Workplace - Health & Safety Executive
• |Workplace Health, Safety & Welfare - general guidance for managers (HSE publication)
• |Heat Stress in the Workplace: What you need to know as an employer (HSE publication)
• |NHS hot weather advice