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temperature but relies on a complex relationship between environmental factors such
as temperature, humidity, air movement, and radiant heat, as well as personal
factors such as the level of activity and insulation afforded by clothing.

When the temperature deviates from the optimum for comfort, employees may
first experience discomfort that is of a subjective nature, but eventually physical
problems that impair health and productivity are incurred. The concept of thermal
comfort is closely related to thermal stress, i.e. heat stress and cold stress.

Heat stress is experienced when the upper tolerance limits of the body are
reached, and employees may suffer from conditions such as heat fatigue, or even heat
stroke with possibly fatal consequences. Cold stress is when the body is unable to
retain enough heat, which may result in, shivering, fatigue, frostbite, confusion, and
loss of consciousness.

The thermal requirements of the Environmental Regulations for Workplaces
make provision for both heat and cold stress, and include the following:

1) Where the WBGT index determined over one hour exceeds 30 °C,
control measures such as medical surveillance, acclimatization and training must be
implemented.
2) Where the dry bulb temperature is taken over a four hour period falls
below 6 °C indoors, or below 6 °C at any time outdoors, reasonable steps must be
taken to protect employees against the cold.
3) Employees working in refrigerated environments must be provided with
thermal protective clothing, medical surveillance, and the time spent in the
refrigerated environment may not exceed the periods prescribed by the regulations.
The wet-bulb globe temperature (WBGT) is a composite temperature used to estimate the
effect of temperature, humidity, wind speed (wind chill), and visible and infrared radiation (usually
sunlight) on humans. It is used by industrial hygienists, athletes, and the military to determine
appropriate exposure levels to high temperatures. It is derived from the following formula:

WBGT = 0,7Tw + 0,2Tg + 0,1Td,
where
Tw - Natural wet-bulb temperature (combined with dry-bulb temperature indicates
humidity);
Tg - Globe thermometer temperature (measured with a globe thermometer, also known as a
black globe thermometer);
Td - Dry-bulb temperature (actual air temperature).
Temperatures may be in either Celsius or Fahrenheit.
Indoors, or when solar radiation is negligible, the following formula is often used:

WBGT=0,7Tw + 0,3Tg.
The WBGT index was developed in 1956 by the United States Marine Corps at Parris Island
to reduce heat stress injuries in recruits; it has been revised several times.

Rationing of the microclimate of industrial premises
The microclimate of industrial premises is normalized according to the
category of work for the severity and period of the year.

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