Thermal Comfort In The Workplace

The temperature and air conditions employees work under and how they react to those conditions significantly influence their productivity and health. In this article, we look at one way of managing these conditions through the concept of thermal comfort.

Why Extreme Temperatures Are An Issue

Working in extreme temperatures can cause some health issues. These can affect the performance of an employee, which in turn can affect safety as their ability to perform tasks or make decisions deteriorates.

For example, employees may take shortcuts to get out of an extreme environment sooner, they may not use personal protective equipment properly to feel more comfortable, or their ability to concentrate on a task may weaken, which increases the chance of errors occurring.

High temperatures can lead to dehydration or heat exhaustion. If the temperature is due to exposure to sunlight, there is also the possibility of sunburn, skin damage, and the risk of developing skin cancer.

Exposure to cold temperatures can lead to frostbite, hypothermia, or can trigger secondary Reynaud’s, a condition that affects the blood supply to parts of the body, usually fingers and toes.

Legal Requirements

The Workplace (Health, Safety and Welfare) Regulations 1992 puts a legal obligation on employers to provide a ‘reasonable’ temperature in the workplace. The law does not impose a minimum temperature in workplaces, but the Regulations do suggest that the temperature in workrooms should typically be at least 16 degrees Celsius, or 13 degrees Celsius if much of the work done in an indoor area requires severe physical effort. The Regulations also do not specify a maximum temperature. However, the TUC has called for a maximum working temperature of 30 degrees Celsius or 27 degrees for those doing strenuous work.

In addition to the above Regulations, the Management of Health and Safety at Work Regulations 1999 require employers to make a suitable assessment of the risks to the health and safety of their workers and take action where necessary and reasonably practicable. Where workrooms must maintain a lower temperature than 16 degrees Celsius for food hygiene purposes, employers should refer to chilled food advice.

Thermal Comfort

Thermal comfort is related to a person’s state of mind regarding whether they feel too hot or too cold.

Six fundamental factors affect thermal comfort, four environmental factors (air temperature, radiant temperature, air velocity and humidity), and two personal (clothing insulation and metabolic heat).

Environmental Factors

1. Air temperature

Air temperature is simply the temperature of the air surrounding the employee measured in degrees Celsius.

2. Radiant temperature

Radiant temperature is due to the heat that radiates from a warm object. It has a more significant influence than air temperature on how we lose or gain heat to the environment.

Radiant heat sources include electric fires, cookers, dryers, ovens, kiln walls, hot surfaces, and molten metals.

3. Air velocity

Air velocity is the speed and direction of air moving across a person. If the speed is low or zero in hot indoor environments, it may cause people to feel stuffy and uncomfortable. Small air movements in cool or cold environments might be perceived as a draught as people are particularly sensitive to these movements. Moving air in warm or humid conditions may help cool people if the air is colder than the environment.

4. Relative Humidity

Relative humidity is the ratio between the amount of water vapour that is actually in the air and the maximum amount of water vapour that the air can hold at that air temperature.

The evaporation of sweat from the skin is the primary way people lose heat from their bodies and maintain a healthy body temperature in hot environments. If relative humidity is above 80% there is so much vapour in the air that it can prevent sweat evaporating, causing workers to become uncomfortably hot.

Humidity in workplace environments can vary greatly. If a workplace is not air-conditioned, or weather conditions outdoors influence the indoor thermal environment, relative humidity may be higher than 70%. Drying processes where steam is given off (for example in a laundry or paper mill) can also produce a high relative humidity.

Personal Factors

1. Clothing insulation

We often use clothing to adapt to our thermal surroundings. We add layers of clothing if we feel cold, or remove layers of clothing if we feel too warm. However, these options are sometimes removed in a work environment because employees are required to wear a specific uniform or Personal Protective Equipment (PPE).

Wearing too much clothing or PPE may cause heat stress, even if the environment is not considered warm or hot. In cold environments clothing that does not provide enough insulation may put the wearer at risk of cold injuries like frostbite or hypothermia.

If non-breathable vapour-impermeable Personal Protective Equipment (for example chemical or asbestos protection suits) is worn, the humidity inside the garment can increase as the wearer sweats because the sweat cannot evaporate.

It is essential to identify how clothing contributes to thermal comfort or discomfort. Employers should periodically evaluate the level of protection provided by existing PPE and evaluating newer types of PPE that are available to see if it is possible to improve the level of thermal comfort.

2. Metabolic Heat

The more physical work we do, the more heat we produce. The more of this metabolic heat we generate, the more it needs to be lost, so we don’t overheat.

The amount of metabolic heat a person produces depends on their size and weight, their age, level of fitness and gender. These can affect their thermal comfort, even when other factors such as air temperature, humidity and air velocity are at acceptable levels.

How to Manage Thermal Comfort

There are four main factors you can control to improve thermal comfort in the workplace.

1. The working environment

There are many ways to control this. It may be a matter of merely replacing hot air with cold, or cold air with hot, whichever is required. If humidity is a problem you can humidify or dehumidify the air as needed. If moving or stagnant air is a problem you can redirect the flow of air using baffles or increase air movement with ventilation or air conditioning.

It may even be possible to separate the employee from the source of heat or cold. Barriers can be installed to shield or insulate the work area. It may be possible to redesign the work area or use alternative equipment that enables the employee to be removed from the area altogether.

2. The tasks

There are three ways to control tasks an employee has to do that can improve thermal comfort. You can restrict the length of time employees are exposed to extreme hot or cold conditions. You can adjust the task itself to change the amount of work and rate of work employees are expected to perform. If an employee has to do physically demanding jobs in warm and hot environments or has to wear a lot of clothing you could use lifting aids or power tools to assist in the task.

3. Clothing

Employers should evaluate a dress code if one exists and allow employees to adapt their clothing where possible. If a uniform must be worn alternative designs, new materials, and other ways to improve the thermal comfort of the clothing should be evaluated. It may be possible to provide multiple layers of clothing so workers can adjust the number of layers they wear based on their individual needs. Employers should ensure their employees wear appropriate PPE and not use a higher protection factor that is necessary.

4. Employee Behaviour

In some situations thermal comfort becomes more controllable when the employee has the freedom to adjust their behaviour and the personal conditions in which they have to work. This may mean allowing employees to adjust thermostats or open windows as appropriate, or organising tasks so their work rate is appropriate to conditions. It may involve providing respite from working conditions in warm-up or cool-down areas or providing personal heaters or fans.

Considering the factors that affect thermal comfort in a workplace is one approach to managing the wellbeing of a workforce. Its importance lies in the fact that air and temperature conditions can have significant effects on productivity, health and safety.