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Temperature and environmental conditions

Temperature and environmental conditions

Whether the mercury is rising or falling, the temperature in which you work can have a significant impact on your health and safety, not to mention your productivity and general comfort.

While there is no legal maximum workplace temperature, employers need to ensure that environmental conditions do not affect workers’ health and safety. This is going to become more important as our weather becomes more extreme.

It is usually accepted that people work best at a temperature between 16°C and 24°C, although this can vary depending on the kind of work being done and the environmental conditions in the workplace – factors such as humidity, clothing and heat sources.

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Risks and health conditions

The legal position

How to tackle it



Risks and health conditions

High temperatures can cause discomfort, dizziness, fainting, lapses in concentration and increased tiredness.

Uncomfortably hot or cold environments can hamper people’s ability to make decisions and perform manual tasks. People may lose concentration, take short cuts to get out of cold environments or remove inappropriate PPE that makes them too hot.

At its most severe, hot and humid work environments can lead to heat stress, which what occurs when the body’s means of controlling its internal temperature starts to fail.

Typical symptoms of heat stress include muscle cramps, heat rash, severe thirst, fainting and heat exhaustion. Heat stroke – which can cause hot dry skin, confusion, convulsions and eventual loss of consciousness – is the most severe disorder and can result in death if not detected early.

People who wear protective clothing while carrying out heavy work in hot and humid conditions could be at risk of heat stress because the PPE can restrict sweat evaporation, preventing the body from losing heat.

Those employed in workplaces where hot processes are carried out – such as boiler rooms, power plants and kitchens – are more at risk of heat stress. Similarly, restricted spaces such as mines and compressed air tunnels present a heat stress risk.

Working outdoors in the sun can be dangerous. It can cause skin damage, including sunburn, blistering and skin ageing and in the long term can increase the risk of skin cancer.

The legal position

Like most health and safety duties, employers’ obligations for managing temperature are set out in general, goal-based terms, which they must work out how to comply with.

Employers should ensure, so far as is reasonably practicable, that temperatures and environmental conditions do not affect workers’ health and safety. If there is a risk that they will, employers must carry out an assessment of those risks and implement measures to control them.

There is no maximum working temperature set down in law. Instead, the Workplace (Health, Safety and Welfare) Regulations (WHSWR) simply state that the temperature in indoor workplaces must be “reasonable”. Employers should consider the work activity and the environmental conditions of the workplace when establishing what this is in practice.

The Approved Code of Practice to the WHSWR elaborates on this, saying that the temperature inside a workplace should provide “reasonable comfort”. It adds that the workplace should be at least 16°C (61°F), or 13°C (55°F) if the work involves rigorous physical effort.

However, if there are work processes that make meeting this minimum unrealistic, such as refrigeration, then employers should ensure that the temperature is as close to these as practical.

During the summer, Prospect often receives reports from members who are sweltering in the heat because the air conditioning system in their workplace has broken down.

The WHSWR states that “equipment, devices and systems” – which will include air conditioning systems – must be “maintained … in an efficient state, in efficient working order and in good repair” and be “subject to a suitable system of maintenance”.

Additionally, the Management of Health and Safety at Work Regulations state that employers have to assess any risks to pregnant women from extremes of heat. The regulations also state that workers under the age of 18 must not be employed in situations where there is a health risk posed by extremes of heat or cold.

How to tackle it

If a significant number of employees are complaining about thermal discomfort, your employer should carry out a risk assessment and act on it.

Hot or cold, thermal comfort is a complex issue, which must take account of multiple factors. HSE guidance says that there are six things to consider when addressing thermal comfort. These are:

  • Air temperature – the temperature of the air surrounding the body.
  • Radiant temperature – the heat generated from objects, such as ovens, cookers, hot surfaces and machinery.
  • Air velocity – the speed of air moving across the employee.
  • Humidity – the amount of water in the air. Relative humidity of over 80% can prevent sweat from evaporating, which is body’s main method of cooling itself.
  • Clothing – in hot conditions, clothing and PPE can prevent sweat from evaporating and is a heat stress risk.
  • Work rate/metabolic heat – the more physical work we do, the more heat we produce. A person’s physical characteristics, such as weight, age and fitness level, can affect thermal comfort.

The HSE has produced a thermal comfort checklist, which employers can complete to help them decide whether they need to carry out a temperature risk assessment. Reps can also use this to help them decide whether they have an issue in their workplace.

The HSE has also produced a checklist for carrying out a heat stress risk assessment.

If the risk assessment reveals that there are problems with thermal comfort or heat stress, then there are a range of simple measures that employers should consider introducing, depending on the six factors outlined above. In hot environments, these might include:

  • ensuring that windows can open, fans are provided, radiators can be switched off and air conditioning units are maintained
  • preventing dehydration by providing cool drinking water
  • introducing rotas, such as flexible hours or early/late starts, to avoid the worst effects of working in high temperatures
  • rescheduling work to cooler times of the day/year
  • providing more frequent rest breaks
  • providing specialised PPE with personal cooling systems or breathable fabrics
  • relaxing formal dress codes
  • insulating hot plant or pipes, or providing air-cooling plant
  • moving workstations away from heat sources or direct sunlight
  • providing workers with training on heat stress symptoms to look out for, safe working practices and emergency procedures
  • identifying who is at risk of heat stress, eg those with heart conditions

If cold environments, control measures might include:

  • issuing appropriate PPE
  • providing facilities for warming up
  • insulating sources of cold
  • excluding drafts from workstations, eg by using baffles
  • encouraging staff to drink warm fluids such as soup or hot drinks
  • introducing more frequent rest breaks
  • delaying work so that it is undertaken at warmer times of the year
  • educating staff about how to recognise the early symptoms of cold stress

Employers can reduce workers’ exposure to sunlight’s damaging ultraviolet light by:

  • Providing suitable protect clothing, such as long sleeved tops and hats with a wide brim
  • Supplying staff with sun cream
  • Arranging more frequent rest breaks
  • Providing shading in work and rest areas
  • Rescheduling work to cooler times of the day


HSE temperature webpages

HSE brief guide to heat stress in the workplace

Heat stress risk assessment checklist

Thermal comfort checklist

HSE guide to health risks from working in the sun