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Keep Cool this Summer

Posted on 10th August, 2020

Over the last few days, we have all had to deal with high temperatures which has made it more difficult to sleep and can often make working uncomfortable as well.  In this article we explain what the law requires employers to do in respect of workplace temperatures and top tips to keep cool this Summer.

The law does not stipulate a maximum workplace temperature due to the high temperatures found in, for example, glass works or foundries. In such environments it is still possible to work safely provided appropriate controls are present. Factors other than air temperature, i.e. radiant temperature, humidity and air velocity, become more significant and the interaction between them become more complex with rising temperatures.

Keep cool this Summer.
How will you keep cool this Summer at work?

The Workplace (Health, Safety and Welfare) Regulations 1992 lay down particular requirements for most aspects of the working environment. In particular, r.7 deals specifically with the temperature in indoor workplaces and states that:

“During working hours, the temperature in all workplaces inside buildings shall be reasonable.”

However, the application of the regulation depends on the nature of the workplace, such as a bakery, a cold store, an office, a warehouse.  It is also worth noting that these Regulations only apply to employees – they do not apply to members of the public, for example, with regard temperature complaints from customers in a shopping centre or cinema.

A simple way of estimating the level of thermal comfort in your workplace is to ask your employees or their safety representatives (such as unions or employee associations) if they are satisfied with the thermal environment i.e. to use a thermal comfort checklist.  A simple checklist is available on the Health and Safety Executive’s website.  The checklist includes an assessment of factors including:

  • Air temperature
  • Radiant temperature
  • Humidity
  • Air movement
  • Metabolic rate
  • Personal protective equipment (PPE)

There are six basic factors which usually cause discomfort which fall into two categories, environmental factors and personal factors.

Environmental factors

Air temperature

This is the temperature of the air surrounding the body. It is usually given in degrees Celsius (°C).

Radiant temperature

Thermal radiation is the heat that radiates from a warm object and may be present if there are heat sources in an environment.  Radiant temperature has a greater influence than air temperature on how we lose or gain heat to the environment.  Examples of radiant heat sources include: the sun; fire; electric fires; ovens; kiln walls; cookers; dryers; hot surfaces and machinery, molten metals etc.

Air velocity

This describes the speed of air moving across the employee and may help cool them if the air is cooler than the environment.  Air velocity is an important factor in thermal comfort for example:

  • still or stagnant air in indoor environments that are artificially heated may cause people to feel stuffy – it may also lead to a build-up in odour
  • moving air in warm or humid conditions can increase heat loss through convection without any change in air temperature
  • physical activity also increases air movement, so air velocity may be corrected to account for a person’s level of physical activity
  • small air movements in cool or cold environments may be perceived as a draught as people are particularly sensitive to these movements


If water is heated and it evaporates to the surrounding environment, the resulting amount of water in the air will provide humidity.  Relative humidity is the ratio between the actual amount of water vapour in the air and the maximum amount of water vapour that the air can hold at that air temperature.  Relative humidity between 40% and 70% does not have a major impact on thermal comfort.

In workplaces which are not air conditioned, or where the weather conditions outdoors may influence the indoor thermal environment, relative humidity may be higher than 70%. Humidity in indoor environments can vary greatly and may be dependent on whether there are drying processes (paper mills, laundry etc) where steam is given off.

High humidity environments have a lot of vapour in the air, which prevents the evaporation of sweat from the skin. In hot environments, humidity is important because less sweat evaporates when humidity is high (80%+). The evaporation of sweat is the main method of heat reduction and helps keep cool in Summer.

When non-breathable vapour-impermeable personal protective equipment (PPE) is worn, the humidity inside the garment increases as the wearer sweats because the sweat cannot evaporate. If an employee is wearing this type of PPE (e.g. asbestos or chemical protection suits etc) the humidity within the PPE will be high.

Personal factors

Clothing insulation

Thermal comfort is very much dependent on the insulating effect of clothing on the wearer.  Wearing too much clothing or PPE may be a primary cause of heat stress even if the environment is not considered warm or hot.  If clothing does not provide enough insulation, the wearer may be at risk from cold injuries such as frostbite or hypothermia in cold conditions.  Clothing is both a potential cause of thermal discomfort as well as a control for it as we adapt to the climate in which we work. You may add layers of clothing if you feel cold or remove layers of clothing if you feel warm. Many companies inhibit this ability for employees to make reasonable adaptations to their clothing as they require them to wear a specific uniform or PPE.

It is important to identify how the clothing contributes to thermal comfort or discomfort. By periodically evaluating the level of protection provided by existing PPE and evaluating newer types of PPE you may be able to improve the level of thermal comfort.

Work rate/metabolic heat

The more physical work that employees do, the more heat they produce. The more heat employees produce, the more heat needs to be lost so that employees do not overheat. The impact of metabolic rate on thermal comfort is critical.

An employee’s physical characteristics should always be borne in mind when considering their thermal comfort, as factors such as their size and weight, age, fitness level and sex can all have an impact on how they feel, even if other factors such as air temperature, humidity and air velocity are all constant.

Practical Steps to Keep Cool this Summer

Employers can help ensure the comfort of their employees in warm conditions. Top tips to keep cool this Summer are:

  1. providing fans, e.g. desk, pedestal or ceiling-mounted fans.  Employers should ensure that the use of such electrical equipment is safe and does not overload electrical circuits
  2. ensuring that windows can be opened. Depending upon the setting, window restraint devices may be required.
  3. shading employees from direct sunlight with blinds or by using reflective film on windows to reduce the heating effects of the sun
  4. siting workstations away from direct sunlight or other situations or objects that that radiate heat (e.g. plant or machinery)
  5. relaxing formal dress code – but you must ensure that personal protective equipment is provided and used if required
  6. allowing sufficient breaks to enable employees to get cold drinks or cool down
  7. providing additional facilities, e.g. cold-water dispensers (water is preferable to caffeine or carbonated drinks)
  8. introducing formal systems of work to limit exposure, e.g. flexible working patterns, job rotation, workstation rotation etc
  9. placing insulating materials around hot plant and pipes
  10. providing air-cooling or air-conditioning plant
  11. Removal of PPE after exposure (and where necessary allowing it to dry out or replace with dry PPE before permitting re-entry) will prevent any heat retained in the clothing from continuing to heat the employee.

Some employers have developed other innovative ideas to keep their staff cool at work.  Jacksons Law Firm recently arranged an ice cream van to visit during the hot weather.  As most of us will be staying in the UK this Summer we must hope that the good weather continues and by making appropriate arrangements in the workplace we should all be able to keep cool.

If you require health and safety advice for your workplace, please contact one of our team.

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