Heat Stress Management in Industries

By | June 9, 2021

Heat Stress Management in Industries:

Heat Stress Management in Industries: Problems of heat stress are very common in some industries such as Iron and steel Mills, glass and Ceramic Units; Forge shops, Foundries, Bricks and Tiles Factories, Thermoelectric plants;  Cements, Coke ovens, Laundries, Mines and many others. There are many work places in thee. units where artificial hot climates are deliberately created for the requirement of some processes. Whenever an individual is exposed to heat stress conditions. There is a resulting strain due considerable changes in many physiological reactions; such as sweat production increased hen rate and higher core temperature etc. The greater the stress level, the greater is the degree of strain experienced.

It is well known that prolonged exposure to excessively high temperatures is a serious hazard to the health of an individual. High heat stress disturbs the thermal equilibrium of the body, and consequently produces many adverse physiological reactions in man. The condition becomes very alarming when high degree of industrial heat combines with the. Metabolic heat arising out of heavy physical work performed by the workmen, particularly during the summer months. Work under such conditions not only produces undue strain and fatigue but also results in progressive decline in efficiency and productivity.

Heat Stress Management

In general terms, the ‘Heat Stress’ of any given working. Situation is considered as the combination of all the factors, both climatic and non-climatic/personal which lead to convective or radioactive heat gain to the body of which .limit or prevent the ‘Heat Dissipative Mechanism” of the body. According to “World Health Organization‘ the “Heat Stress’ is the load of heat that must be dissipated by the body, if it is to remain in thermal equilibrium.

Heat-exchanges phenomena and heat-balance:

The environmental heat load results basically from two mechanisms. ‘conduction convections and radiation, R. Besides, the human body generates heat due to intracellular oxidative processes (metabolism), the metabolic heat, M. a combination of heat generated by the basal metabolism and that resulting from physical activity?

In order that the body maintains internal thermal balance, the metabolic heat load must dissipated and this can achieved, through conduction,” convection and radiation. (Depending on environmental conditions, the body may gain or loss heat through these mechanisms). In addition, heat can also be lost by the body through another mechanism the evaporative cooling (E), which the cooling effect of the evaporation of perspiration from the skin (the evaporation of one liter of sweat removes 580 kcal heat from body to the surrounding environmental)

Heat Balance in Heat Stress Management:

Heat exchanges between the human body and its environment follow certain physical laws and can expressed by mathematical equation, popularly known as the heat balance equation which can represented as follows:


Where M is the ‘heat of metabolism depending on the amount of physical activity involved in the task.

 C= Convective heat gain or loss

R= Radiant heat gain or loss.

Both C & R depend on the climatic conditions, of the work environment

E = Evaporative heat loss,

it partly depends on the rate of sweating and partly on climatic conditions of work environment, especially the humidity and vapor pressure on the surface of the skin. Sweat produced on to the surface of the skin gets evaporated when the vapor pressure 6- the skin higher than that of the surroundings. Providing relief to the individuals. Air movement enhances evaporative heat loss.

S= Amount of heat gain or loss by the body.

When heat balance, there is no storage of heat (S = 0 and accordingly the equation may represented as:

M±C±R-E =0 (or MEC+R == E)

This would mean that heat generated internally, as well as heat received from Ute external environment through convection and radiation could be dissipated solely by evaporation of &. What Obviously the sweat production should be much increased and this situation would place a definite strain on the human body.

Factors Responsible for Heat Balance:

  1. Climatic
  2. Non-Climatic

Heat Stress Management in Industries

Climatic Factors:

Environment factors determine as to how, and as to what extend the metabolic heat can be lost to the outside environment, or as to how and as to what extend the body will gain heat from the environment around since:

C-Depends on ambient air temperature and movement of air.

R-Depends on the mean radiant temperature of hot equipment or process heat.

E-Depends on ambient air temperature, humidity and air movement.

The thermal environment (Climatic factors), therefore comprises the four climatic parameters:

  1. air temperature,
  2. air humidity;
  3. radiant heat.
  4. air movement,

The above parameters needs to measured simultaneously and at the same spot considering the locations of the workers exposure.

Non-climatic factors in Heat Stress Management:

In ‘addition to the climatic factors as stated above there are also other factors (Non-climatic) to reckon with

  • The ‘rate of work’
  • Whether or not an individual acclimatized,
  • The amount and type of clothing work’,
  • Physical fitness level of the individual workers
  • ‘Age’,
  • Sex, etc.

Which are likely to modify the level of discomfort or distress, and consequently the heat strain’ developed among the individuals exposed to such environment.

Measurement of heat stress:

Heat has been on record as a hazard to man since biblical times. However, only in the late few decades that national means have developed for evaluating the stresses of hot environment identifying the contributing factors .and predicting the resulting physiological stain,

Air Temperatures: The air temperature expressed in degrees Celsius (OC); or degree Fahrenheit (OF), and can measured with the help of mercury thermometers; thermocouples, thermostats and resistance thermometers. The mercury thermometers most widely used which very simple, and more convenient than other types, particularly from the cost point of view, but very fragile requiring care in handling.

Air Humidity: The air humidity can by estimated from the absolute and relative humidity values. Whereas the absolute humidity indicates the actual amount of water vapor in the air; (expressed in grams of water vapor per cubic centimeter); relative humidity is the percentile ration of the amount of moisture present in the air and the amount of moisture; present in the air and the amount that the air could hold if saturated and at the same temperature.

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