10.1 b Temp. and Thermal Environment Flashcards Preview

B10. Work environment risks and controls > 10.1 b Temp. and Thermal Environment > Flashcards

Flashcards in 10.1 b Temp. and Thermal Environment Deck (10):

Heat stroke is imminent when the core body temperature exceeds



Cold environments Four factors contribute to cold stress:

 cold temperatures  high or cold winds  dampness  cold water


Guidance on heat stress from the Australian Institute of Occupational Hygienists (AIOH) highlights the following adverse health effects: 5

 heat stroke  heat exhaustion  heat syncope (fainting)  heat cramps  prickly heat (heat rash).


The first effect of excessive heat strain due to cold environments is pain. This is followed by numbness of the extremities, especially the fingers and toes, as the body shunts warm blood to the core, away from the non-vital extremities, such as the hands, feet, nose, cheeks and ears. The effects include: 4

 chilblains  frostbite  immersion foot (trenchfoot)  hypothermia (which may be mild, moderate, or severe).


Mild hypothermia

36.5 – 32 °C


Moderate hypothermia

32 – 30°C


Severe hypothermia

30 – 25.5°C


The effects and severity of heat strain on individuals depends on the physiological capacity of the individual, as influenced by the following personal factors: 8

 age  gender  general health (including medical conditions, weight and general fitness etc.)  state of hydration  alcohol, caffeine and diet  nicotine use  medications and non-prescription drugs  acclimatisation and protective clothing and other protective equipment.


Thermal surveys - measurement equipment The external variables of interest in determining thermal comfort are:

 air temperature  mean radiant temperature  relative humidity  air flow.


The mean radiant temperature is

The mean radiant temperature is the temperature of a uniform enclosure, with which a small black sphere at the test point would have the same radiation exchange as it does with the real environment. Measurement of the mean radiant temperature can be derived from the readings of a black globe thermometer. This consists of a hollow black globe, usually made of copper (due to its high conductivity), in the centre of which is placed a temperature sensor. The standard 150mm black copper globe takes about 20 minutes to reach equilibrium, but this can be reduced by increasing air movement within the globe, and by using thermocouples instead of mercury-in-glass thermometers. Because of its high inertia, the black globe thermometer cannot be used to determine the radiant temperature of environments that vary rapidly.