Module 1: Occupational Hygiene - Section 5: Instrumentation
OH5.8: Evaluation of Thermal Stress - Introduction

Introduction:

Thousands of workers around the country work in conditions which expose them to hot or cold environments. Extremes of temperature affect the amount of work people do and the manner in which they do it. In many workplaces the problem is often high temperatures rather than low temperatures.

The main sources of heat in industry are extremely hot or molten materials (bakeries, foundries, smelters, steel mills) and summer sunshine (construction, agriculture, surface mining).

Physiological effects of heat:

The human body maintains a fairly constant internal temperature, even though it is being exposed to varying environmental temperatures. This is achieved by maintaining a balance between the amount of heat gained by the body and that released from the body.

When body temperature increases, blood circulates closer to the surface of the skin, and the excess heat is lost to the cooler environment.

When body temperature drops, blood moves to the centre (core) of the body and this cuts down the amount of heat lost. If temperature continues to drop, the body starts shivering to generate heat.

Heat stress factors:

Heat stress is the aggregate of internal and external heat load factors on the body.

Heat strain is the sum of all biochemical, physiological, psychological and pathological adjustments in the person in response to heat stress.

External (thermal environment) factors: Internal (body) factors:

REFERENCES:

  1. Schoeman JJ. Temperature Extremes. In: Occupational Hygiene. Edited by Schoeman JJ and Schroeder HHE. Published by Juta & Co., 1996.
  2. Parsons KC. Assessment of Heat Stress Indices. In: Encyclopaedia for Occupational Health and Safety, Fourth Edition. Published by the International Labour Office, 1998.
  3. Ogawa T. Heat Disorders. In: Encyclopaedia for Occupational Health and Safety, Fourth Edition. Published by the International Labour Office, 1998.
  4. Working in Hot Environments - Health Effects. Canadian Centre for Occupational Health and Safety. .
  5. Working in Hot Environments - Control Measures. Canadian Centre for Occupational Health and Safety. .
  6. American Conference of Governmental Industrial Hygienists. Documentation of Threshold Limit Values and Biological Exposure Indices. Latest Edition.




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General Introduction to Occupational Health: Occupational Hygiene, Epidemiology & Biostatistics by Prof Jonny Myers is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License
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