Information about how the temperature of the environment you work in can affect you and advice on how to manage it (closely based on material developed by the British Health and Safety Executive [HSE]).
NOTE: There are no set temperatures above which or below which work is not permissible. The reason for this, as you will see in this guidance material, is that air temperature is only one of the determinants of thermal comfort.
Workplace temperature and thermal comfort
Are you or your workers feeling uncomfortable with the temperature in the workplace?
The term ‘thermal comfort’ describes a person’s state of mind in terms of whether they feel too hot or too cold.
There’s more to it than just room temperature. Environmental factors (such as humidity and sources of heat in the workplace) combine with personal factors (such as the clothing you’re wearing and how physically demanding your work is) to influence what is called your ‘thermal comfort’.
These pages looks at what we mean by thermal comfort in the workplace and what the law says. It provides guidance for persons conducting a business or undertaking (PCBU) to help them conduct a thermal comfort risk assessment, using the ‘Five steps to risk assessment’ approach. It also contains information for workers, and should help them suggest ways of improving thermal comfort in their workplace.
The guidance is directed primarily at PCBUs but we are also keen to have the reactions of workers. Health, safety and welfare are best ensured by workers and PCBUs working together to assess and manage risks.
The Work Health and Safety Regulation 2011 does not address thermal comfort explicitly, but places more specific obligations on a PCBU in relation to the work environment and facilities for workers, including requirements to:
Thermal comfort is defined as: ‘that condition of mind which expresses satisfaction with the thermal environment.’
So the term ‘thermal comfort’ describes a person’s psychological state of mind and is usually referred to in terms of whether someone is feeling too hot or too cold.
Thermal comfort is very difficult to define because you need to take into account a range of environmental and personal factors when deciding what will make people feel comfortable. These factors make up what is known as the ‘human thermal environment’.
The best that you can realistically hope to achieve is a thermal environment that satisfies the majority of people in the workplace, or put more simply, ‘reasonable comfort’. Though there is no absolute rule, 80% of occupants might be considered a reasonable limit for the minimum number of people who should be thermally comfortable in an environment.
So, thermal comfort is not measured by air temperature, but by the number of employees complaining of thermal discomfort. To better understand why air temperature alone is not a valid indicator of thermal comfort, see the six basic factors.
Because thermal comfort is psychological, it may affect our overall morale. Worker complaints may increase, productivity may fall and in some cases people may refuse to work in a particular environment. Some aspects of the thermal environment, such as air temperature, radiant heat, humidity and air movement, may also contribute to the symptoms of sick building syndrome.
People employ adaptive strategies to cope with their thermal environment, e.g. donning or removing clothing, unconscious changes in posture, choice of heating, moving to cooler locations away from heat sources, etc.
The problems arise when this choice (to remove jacket, or move away from heat source) is removed, and people are no longer able to adapt. In many instances, the environment within which people work is a product of the processes of the job they are doing, so they are unable to adapt to their environment.
The most commonly used indicator of thermal comfort is air temperature – it is easy to use and most people can relate to it. But although it is an important indicator to take into account, air temperature alone is neither a valid nor an accurate indicator of thermal comfort or thermal stress. Air temperature should always be considered in relation to other environmental and personal factors.
The six factors affecting thermal comfort are both environmental and personal. These factors may be independent of each other, but together contribute to a worker’s thermal comfort.
Environmental factors :
Personal factors :
1. Air temperature
This is the temperature of the air surrounding the body. It is usually given in degrees Celsius (°C) in Australia.
2. Radiant temperature
Thermal radiation is the heat that radiates from a warm object. Radiant heat 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. Our skin absorbs almost as much radiant energy as a matt black object, although this may be reduced by wearing reflective clothing.
Examples of radiant heat sources include: the sun; fire; electric fires; furnaces; steam rollers; ovens; walls in kilns; cooker; dryers; hot surfaces and machinery, molten metals etc.
3. Air velocity
This describes the speed of air moving across the worker and may help cool the worker if it is cooler than the environment.
Air velocity is an important factor in thermal comfort because people are sensitive to it.
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.
Small air movement in cool or cold environment may be perceived as draught. If the air temperature is less than skin temperature, it will significantly increase convective heat loss.
Physical activity also increases air movement, so air velocity may be corrected to account for a person’s level of physical activity.
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 n 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 some offices, humidity is usually kept between 40-70% because of computers. However, in workplaces which are not air conditioned, or where the climatic conditions outdoors may influence the indoor thermal environment, relative humidity may be higher than 70% on warm or hot humid days. Humidity in indoor environments can vary greatly, and may be dependent of 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 loss in humans.
When 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 microclimate of the garment may be high.
5. Clothing insulation
Clothing, by its very nature, interferes with our ability to lose heat to the environment. Thermal comfort is very much dependant on the insulating effect of clothing on the wearer.
Wearing too much clothing or personal protective equipment (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 frost bite 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 live and play. You may add layers of clothing if you feel cold, or remove layers of clothing if you feel warm. However, some businesses remove the ability of their employees to make reasonable adaptations to their clothing.
It is important to identify how the clothing may contribute to thermal comfort or discomfort. It may also be necessary to evaluate the level of protection that any PPE is providing – can there be less, or other, PPE used?
6. Work rate / metabolic heat
The work or metabolic rate is essential for a thermal risk assessment. It describes the heat that we produce inside our bodies as we carry out physical activity.
The more physical work we do, the more heat we produce. The more heat we produce, the more heat needs to be lost so we don’t overheat. The impact of metabolic rate on thermal comfort is critical.
When considering these factors, it is also essential to consider a person’s own physical characteristics.
A person’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.
A simple way of estimating the level of thermal comfort in your workplace is to ask the workers or their workplace representatives, such as unions or employee associations. If the percentage of workers dissatisfied with the thermal environment is above a certain level, you will need to take action. See the six steps to risk assessment for more details.
If you wish to measure thermal comfort in a more scientific manner, please refer to the relevant Australian standards relating to thermal comfort.
Use the table below to help you identify whether there may be a risk of thermal discomfort to your workers. Please note that this is a basic checklist and does not replace an adequate thermal comfort risk assessment. Read the descriptions for each thermal comfort factor, and answer YES or NO. If you have two or more ‘YES’ answers, there may be a risk of thermal discomfort and you may need to carry out a more detailed risk assessment.
Factor / Description
What your workers think
In most instances, the guidance given on this website will be sufficient to enable you to improve thermal comfort in your workplace. However, you may wish to measure the factors contributing to thermal comfort more accurately. In that case you should seek the guidance and support of suitably qualified professionals.
There are a number of ways that you can manage thermal comfort in the workplace:
Administrative controls include planning and rescheduling work times and practices and rest schedules. For example, scheduling ‘hot’ work for cooler times of the day or giving workers flexible hours to help avoid the worst effect of working in high temperatures. Administrative controls are generally of a short term, temporary nature and are also widely recognised as being more expensive and less cost-effective than engineering controls in the long-term.
These should be the first choice to reduce or eliminate the hazard. Although the initial cost of engineering controls seems high, it has been found that the implementation cost is often offset by the resulting improvements to production and decrease in down time, with reduced absenteeism and improved motivation.
It is important to stress that any practical solution to controlling thermal comfort is likely to require a combination of different options alongside consultation between PCBUs, workers and their representatives.
Many types of heating systems are available:
Most of these systems are useful. However, the beneficial effects may be in some situations restricted to the immediate locality of the heat source.
There are many methods for increasing air movement. Small ‘personal’ fans can provide a refreshing movement of air on the face. Larger oscillating fans can provide a swirling air movement, though some people may find this draughty. There may also be noise problems.
Large diameter fans suspended from the ceiling can provide a swirling air movement that is effective over a wide area. Exhaust fans, mounted in the roofs and walls, are useful for removing heated air; however, while improving general air movement, they may have little effect on thermal comfort.
This can range from small units that lower the air temperature but do not control humidity levels or air movement, to large units that can cope with extreme conditions as well as humidity and air movement.
When air conditioning systems are used, care should be taken to ensure uniform air distribution throughout the workplace, otherwise some workers may complain of feeling cold while others are feeling hot.
Air conditioning units should be operated as per the manufacturer’s instructions.
Evaporative coolers produce a moderate reduction in air temperature and increase humidity. They operate by passing hot air over water-saturated pads and the water evaporation effect reduces the air temperature.
There are many different types of thermal insulation materials, eg loose fills, rock wool and boards. The material acts as a barrier, which slows heat flow in the summer and heat loss in the winter, but it is only effective where there is a temperature difference between the inside and the outside of the building or between two areas inside a building.
Generic control measures
There are eight main methods of control which you can use:
1. Control the heat source
2. Control the environment
3. Separate the source of heat or cold from the worker
4. Control the task
5. Control the clothing
6. Allow for the worker to make behavioural adaptations
7. Protect the worker
8. Monitor the worker
This section outlines your responsibilities as a PCBU, and suggests some ways you can improve thermal comfort in the workplace.
Managing thermal comfort in the workplace
In organisations where thermal discomfort in indoor environments is a risk, it is vital that management provides a visible commitment to the health and well-being of their workers.
In many workplaces, thermal discomfort may only occur during unscheduled repair and maintenance work, when heating ventilation and air conditioning systems either break down or don't work as intended, eg during the hottest or coldest months. When this occurs, it is important to consider the possible impact of increased thermal discomfort on workers.
It is the responsibility of management to ensure that a business or undertaking adapts as necessary to reduce or eliminate the risk of thermal discomfort amongst the workers.
If thermal discomfort is a risk, and your workers are complaining and/or reporting illnesses that may be caused by the thermal environment, then you should develop a thermal comfort programme:
When people are too hot
You can help ensure thermal comfort in warm conditions by:
When people are too cold
You can help ensure thermal comfort when working in the cold by:
PPE and thermal comfort
Personal protective equipment (PPE) is considered to be a ‘last resort’ to protect workers from the hazards in the workplace.
PPE reduces the body’s ability to evaporate sweat. Additionally, if the PPE is cumbersome or heavy it may contribute to an increase in the heat being generated inside the body.
Wearing PPE in warm/hot environments and/or with high work rates may increase the risk of thermal discomfort and heat stress.
Removal of PPE after exposure will prevent any heat retained in the clothing from continuing to heat the worker.
PPE may prevent the wearer from adapting to their environment by removing clothing because to do so would expose them to the hazard that the PPE is intended to protect them from. However, people may not wear their PPE correctly (e.g. undo fasteners to increase air movement into the garment) and thereby expose themselves to the primary hazard.
This section outlines what you can do if you think there is a thermal comfort problem in your workplace. It is important for you to report any problems you come across to your management, union or other workplace representative. It may be that you have to work with your management and fellow workers to get permission to take some of the steps below, but by working together, it is more likely that suitable, long term solutions to any problems can be found.
What can you do?
There are a number of things that you can do to improve thermal comfort in your workplace:
Although any of the actions outlined above may go some way to alleviating your thermal discomfort, there are also a number of things that your manager or employer could do to help further.
Talk to your manager, supervisor, union representative or worker representative about: