Thermal Comfort Definition

The Thermal Comfort Definition is very difficult to define. This is because you must consider a variety of environmental and personal factors when deciding which temperatures and ventilation will make employees comfortable. Essentially, the more extreme the environment, the greater the risk for workers to expose to serious illness and injury, even death.

Thermal discomfort can seriously affect a worker’s overall morale and job performance. Prolonged exposure can cause fatigue, and decreased concentration and productivity. In addition, complaints and absenteeism of workers can increase. But what exactly is thermal comfort? The ISO 7730 standard defines thermal comfort definition as a mental condition that expresses satisfaction with the thermal environment”. This definition may satisfy most people, but it is also a definition that is not easy to translate into physical parameters.

The complexity of evaluating the Thermal Comfort Definition can be illustrated with an example: On a cold and sunny winter day, a normally dressed person may rest in a heated room, while another lightly clothed person may be playing sports on the Exterior.

Both people can feel comfortable even if they are in totally different thermal environments. This reminds us that thermal comfort depends on many physical parameters, rather than just one, such as temperature.

What is the Thermal Comfort Definition?

The thermal environment of the workplace is a factor that can negatively influence the well-being of workers. Although it is not extreme, even in moderate thermal environments there are workers who feel comfortable while others feel hot or cold (e.g., with air conditioning). For this reason, thermal comfort refers to a sensation of thermal neutrality for the whole body. However, the lack of thermal well-being can take place in the whole body or one part of the body.

Thermal Comfort Definition
Thermal Comfort Definition

Thermal Comfort Definition is defined as sensory satisfaction with the thermal environment. Such comfort conditions are very important in the work environment. That is, the physical and psychological well-being of people when the conditions of temperature, humidity and air movement are favourable to the activity that is carried out.

The human body produces heat continuously to maintain a constant internal temperature, located around 37º C. The excess heat is transferred to the surrounding environment, generally through the skin, thanks to the fact that we have thermoregulation mechanisms whose function is to allow the body to maintain its thermal equilibrium.

Self-regulation mechanisms

The self-regulation mechanisms by which people receive or give up the heat, which prevents the rise in internal temperature, are mainly:

  • Perspiration or evaporation through sweating. It can depend on humidity (higher humidity means less sweating), airspeed (faster speed, more evaporation), temperature (more sweating at higher temperatures) and clothing. 
  • Convection or heat exchange, until the temperature between the body and the air or water around it, is balanced. If the air temperature is higher than that of the body, there will be a transfer of heat to the body. If the temperature was lower, the heat transfer will take place from the body to the external environment, with the consequent loss of heat from the body. 
  • Radiation or emission and absorption of energy from objects (ovens, stoves, etc.), depending on the temperature of said objects. 

Why thermal comfort is important?

The human organism needs to maintain its internal temperature within a narrow range of oscillation to guarantee the correct functioning of vital functions, determined by the combination of thermo-hydrometric variables with the intensity of the activity carried out at work.

Thermal Comfort Definition
Thermal Comfort Definition

An unsuitable thermal environment can cause a reduction in physical and mental performance, with a consequent decrease in productivity, and an increase in distractions, due to the inconvenience caused, and these distractions may be the cause of workplace accidents. In some situations, the thermal environment can become a serious threat to health (e.g., working in freezing rooms or foundries). 

Human comfort meaning

The types of clothing and the individual characteristics of the workers, always entail a significant subjective burden and, consequently, the impossibility of accurately defining the factors of a comfortable environment. 

Very intense thermal aggression can have fatal consequences on the human organism; therefore, in extreme situations, it is necessary to strictly limit the time spent in such conditions. 

The environmental conditions in the workplace (air temperature, thermal radiation, humidity and airspeed) together with other parameters that influence the thermal balance of the body (heat generated by the physical activity carried out, thermal insulation of clothing) can cause risk situations for the health of workers, either due to heat or cold.

Thermal stress is the net heat load or cold to which workers are exposed and resulting from the combined contribution of environmental conditions where they work, physical activity performed and the clothes they wear.

Effect of temperature on human body

The most notable conditions or effects of heat stress are:

Heat strokes occur when the system that controls the body’s temperature falls and perspiration becomes inadequate: The skin will be very hot, dry, red, or blotchy, and the affected person will present symptoms of confusion and disorientation and even loss of consciousness or seizures and your temperature will be 40.5 ° C or higher.

Thermal Comfort Definition
Thermal Comfort Definition

Heat exhaustion, when losing large amounts of fluid through perspiration and, occasionally, excessive loss of salt: the skin will be moist, pale or reddened, and the affected person will feel extreme weakness or fatigue, dizziness, nausea and headache and even loss of consciousness and your temperature will be normal or slightly high. As preventive measures, we find:

  • Make him rest in a cool place and consume large amounts of fluids.
  • Offer you medical assistance if you do not recover. 

Heat cramps are painful spasms of the muscles due to profuse sweating combined with the intake of large amounts of water, diluting the body fluids while the body continues to lose salt, which can cause painful cramps, during or after hours of work.

Preventive measures: consume isotonic drinks or liquids rich in salt.

Fainting from exposure of the worker to high temperatures, especially when standing still. Preventive measures: rest lying down in a cool place. Rash, due to difficulties in eliminating perspiration, which causes the skin to remain moist for long periods. Preventive measures: schedule breaks in cool places and heat rashes and dry the skin well.

The effects of cold stress such as hypothermia, trench foot, chilblain etc. 

What is thermal comfort temperature?

The dry air temperature is defined as the temperature of the air that surrounds the individual. The difference between this temperature and that of people’s skin determines the heat exchange between the individual and the air. This exchange is called “heat exchange by convection.” There is also the exchange of heat by radiation between some and other surfaces of the environment (skin, machines, glass, walls, ceilings, etc.).

This makes, for example, it can be pleasant to be in a house where the temperature is 15º C, but its walls are at 22º C. If the temperature of the skin is higher than the average radiant temperature, the body transfers heat by radiation to the environment. If it is lower the body receives heat from the environment. 

Thermal comfort depends on the heat produced by the body and the exchanges between it and the environment. Health & Safety Executive advises that no meaningful figure can be given for maximum workplace temperatures (due to high temperatures found, for example, in glassworks or foundries). The Workplace Regulations ( Health, Safety and Welfare) of 1992 impose a legal obligation on employers to provide a “reasonable” temperature in the workplace.

Universal Thermal Comfort Index

WBGT index = 82.0 – 84.9 ° F. Discretion should be used when planning heavy exercises for inexperienced personnel. It is sometimes used as a marginal limit for environmental heat stress. 

WBGT Heat Index

85.0 – 87.9 ° F    Avoid strenuous exercise

85.0 ° F or more avoid working in direct sunlight

88.0 ° F  restriction of strenuous exercise

90.0 ° F or more suspension of strenuous exercise

factors that affect thermal comfort

Clothing: Thermal comfort is highly dependent on the insulating effect of clothing on the wearer. Wearing too much clothing or PPE can be a leading cause of heat stress, even if the environment is moderate, not warm or hot. If clothing does not provide sufficient insulation, the user may be at risk of cold injuries, such as frostbite or hypothermia in cold conditions. Clothing is both a possible cause of thermal discomfort and control of it as we adapt to the climate in which we work.

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You can add layers of clothing if you feel cold or remove layers of clothing if you feel hot. It is important to identify how clothing contributes to thermal comfort or discomfort. By regularly evaluating the level of protection provided by existing PPE.

The problem with this process is that when ambient temperatures outside the body get closer to normal skin temperature. The cooling process becomes more difficult. The sweat glands pour electrolyte-containing fluids onto the surface of the skin.

Thermal Comfort Definition
Thermal Comfort Definition

And the evaporation of sweat becomes the main effective means of cooling. Workers who must perform delicate or detailed work may see their accuracy diminish. And others may see their compression and retention of information diminished. 

 1. Air temperature:

  • Locate sources of heat or cold in the periphery.
  • Eliminate sources of hot or cold air.
  • Insulate hot surfaces. 
  • Localized extraction of hot or cold air.
  • Ventilate avoiding drafts. 
  • Wear clothing with little or a lot of thermal insulation. 
  • Drink liquids before, during and after exposure to the sun, in greater quantity and frequency. 
  • Avoid the consumption of alcohol and stimulating drinks.

2. Humidity:

  • Eliminate steam and water leaks.
  • Enclose surfaces cooled by evaporation of water and the cooling system.
  • Wear clothing that is waterproof but vapour-permeable to allow sweat to evaporate.

3. Thermal radiation:

  • Reduce radiating surfaces.
  • Install reflective screens.
  • Insulate or treat radiating surfaces.
  • Locate workstations away from radiant surfaces.
  • Wear special protective clothing that reflects radiation.
  • Use sun protection cream.

4. Physical workload:

  • Mechanize work.
  • Reduce movements at work and their speed.
  • Reduce commuting.
  • Reduce efforts.
  • Improve posture.

5. Clothes:

  • Improve clothing design.
  • Select suitable fabrics and materials.
  • Look for lightweight fabrics and materials.
  • Wear a wide-brimmed hat or cap, refreshing yourself from time to time with water.
  • Use gloves.

6. Organization of work:

  • In hotter times, reduce the time of exposure to the sun, trying to avoid the time slot between 12 and 17 hours. In cold weather, carry out work outdoors during the hours of greatest sun exposure. 
  • Perform the tasks that require the most effort first thing in the morning.
  • Plan breaks periodically in shaded places. 
  • Take breaks and rest whenever necessary.
  • Schedule rotations to carry out tasks that involve special physical effort or greater risk, limiting the time spent on them. 

How do you control thermal comfort?

  • Control other environmental parameters are:
  • Replace warm air with cold or replace cold air with warm, as needed
  • Humidify or dehumidify the air as needed
  • Increase air movement through ventilation or air conditioning.
  • Job design, including job rotation
  • Introducing mechanical aids (for example, lifting aids or power tools) to assist in physically demanding jobs in hot. Because of hot environments or when employees wear a lot of clothing.
  • Consider alternate shift patterns or work schedules, ie earlier start and end times
  • Provide hot/cold drinks
  • Make beverages available and encourage employees to take an extra break
  • Employers must provide an adequate supply of cold potable water near the work area for workers exposed to heat. Employees must drink small amounts frequently; for example, one cup every 30 minutes. Liquids that contain caffeine or alcohol are not appropriate because they increase dehydration.
  • Drink hot and sweet beverages and avoid caffeinated or alcoholic beverages to avoid cold stress. Add soups and other high-calorie foods to your diet.


The key to preventing heat/cold stress is educating employees about the dangers of working in extreme temperatures. And the benefits of implementing proper work practices and controls. The employer must provide information on:

  • Signs/symptoms of heat/cold-related illness. Employees must recognize dehydration, exhaustion, fainting spells, heat cramps, heat exhaustion, heatstroke as heart disorders and trench foot, chilblain etc.
  • Factors that affect a person’s sensitivity to heat/cold, such as age, weight, and types of medications.

Employee responsibilities

Prevention strategies include the implementation of engineering controls, acclimatization, and reduction of physical demands. Moreover, alternation of work and rest periods, and fluid replacement.

Health and safety-related topics:

  1. fire extinguisher inspections requirements
  2. 5 types of workplace hazards
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  4. Alcohol and drug test at work
  5. Scaffold safety requirements
  6. Heat stress hazards and control measures
  7. Housekeeping hazards on construction site
  8. Unsafe act and unsafe condition difference



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