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Feeling hot, hot, hot: what's the maximum legal temperature staff can work in?

The Met Office issued a rare Level 4 - Emergency heat warning for parts of England from Monday 18 July with temperatures predicated to rise in some places to 40 degrees. 

A red warning is only given where a heatwave is so severe and/or prolonged that its effects extend outside the health and social care system. At this level, illness and death may occur among the fit and healthy, and not just in high-risk groups. . 

Regulation 7 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires employers to ensure that the temperature in their workplaces is "reasonable". Contrary to popular opinion, there are no legal minimum or maximum working temperatures.

So what does "reasonable" mean?

Guidance issued by the HSE, suggests that temperatures should be "at least" 16°C' or 13°C if much of the work involves rigorous physical effort, but it doesn't set a limit on maximum temperatures. This is because certain workplaces (glass works, launderettes, bakeries etc) will always be far hotter than most other workplaces. But it states that even where staff are working in very hot environments, they can still work safely "provided appropriate controls are present". 

What's reasonable will therefore vary from workplace to workplace and the HSE recommend that you take the following steps to assess risk: 

1. Carry out a thermal comfort risk assessment

This isn't just about recording the temperature. You'll need to consider air movement, radiant temperature, humidity and the type of clothing staff have to wear. There are 17 questions to answer and HSE recommend that if you answer yes to two or more, there is a risk of "thermal discomfort" and you may need to carry out a more detailed risk assessment.  

It's already very hot and, if you haven't already considered these issues, you may not have time to complete a full thermal comfort risk assessment. So, if your staff are complaining about the heat, it's probably sensible to assume that your workplace might be creating heat stress in some people and look at ways to reduce this.  

If you are working in a heat stress situation you should use the heat stress checklist (PDF)

2. Act on the findings of the risk assessment by implementing appropriate controls 

Once you've considered the risk, you need to take steps to reduce it in the same way you would in respect of any other health and safety issue. 

In the context of a heat-wave, you will only have to make changes on a temporary basis.  

What is heat stress?

Heat stress occurs when the body’s means of controlling its internal temperature starts to fail. Air temperature, work rate, humidity and work clothing are all factors which can cause heat stress.  

Signs of heat stress include: 

  • an inability to concentrate
  • muscle cramps
  • heat rash
  • severe thirst – a late symptom of heat stress
  • fainting
  • heat exhaustion – fatigue, giddiness, nausea, headache, moist skin
  • heat stroke – hot dry skin, confusion, convulsions and eventual loss of consciousness. This is the most severe disorder and can result in death if not detected at an early stage.  

Five practical steps to reduce heat stress 

The easiest solution for many workplaces is to use fans and air conditioning units to cool the ambient temperate and, where possible, use physical barriers that reduce exposure to radiant heat. But, if you can't do this, consider these options:

  1. Recognise that heat causes fatigue and adjust the work rate to allow staff to slow down and take more frequent rest breaks 
  2. Adjust working hours so that staff can work at cooler times of the day
  3. Provide access to cool drinking water and encourage staff to rehydrate frequently
  4. Relax your uniform policies so that staff can work more comfortably 
  5. Monitor any employee who is more susceptible to heat stress because of an illness, condition or medication. This is likely to include pregnant and menopausal women or those with heart conditions. Consider what reasonable adjustments you can make such as allowing them to work from home or adjusting their working hours 

Need help?

Please contact Glenn Hayes if you need help assessing risk or responding to complaints from staff. 

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This article was updated on 18 July 2022.