Heat Stress is the total load of heat on the human body resulting from work activity and environmental conditions. Heat Strain occurs when the body’s core temperature rises above 38°c due to total heat load. Symptoms of heat stress in hot conditions are varied but include sweating, dehydration, prickly heat, exhaustion and in extreme cases may cause delirium, disorientation and death.
Factors Causing Heat Stress
The human body has regulatory mechanisms to control its core temperature in response to environmental and human factors including Air Temperature, Humidity, Air Speed, Radiant Temperature, Metabolic Heat Produced by the Body, Skin Temperature, Clothing, Number and Duration of Heat Exposures and Thermal Conditions of Rest Areas.
The combination of these factors will determine the heat stress placed on each person in a working environment.
Measurement of Heat Stress
Indicators of heat stress used by occupational hygienists include the Wet Bulb Globe Temperature Index (WBGT), Heat Stress Index (HSI) and Sweat Rate Required (SWR).
Each of the above indicators of heat stress have permissible heat exposure limit values. A qualified Environmental Health Solutions (EHS) occupational hygienist would measure the appropriate heat stress parameters, compare them to relevant exposure guidelines and recommended control measures where appropriate.