Severe and extreme heatwaves in Australia have caused more deaths than any other natural disaster in the last 200 years according to the Australian Bureau of Meteorology. The official death toll of the 2009 Victorian Black Saturday bushfires was 173, but 374 people died from heat-related causes during the heatwave that preceded it.
OHSA has conducted heat stress monitoring at a variety of workplaces including:
Setting of a safe/unsafe limit simply based on ambient air temperature is not appropriate due to the many variables (i.e. task, environment and individual) associated with the onset of heat strain. as guides.
Identification and assessment
Identifying and managing heat stress is not just about the air temperature. Assessing risks of heat related illness requires accurate identification and assessment of:
Conduct a walk through survey of the workplace, and ask your workers about their heat stress issues. Consider the work location’s previous history of heat stress issues, including what time of day or year and under what circumstances they occurred.
Some standard questions in any heat investigation include:
Use the following three level approach to identify heat stress factors in your workplace (Di Corleto et al 2013).
Level 1 (Non-technical): is a basic risk assessment, which can use a simple index such as the Heat stress (basic) calculator.
Heat stress (basic) calculator is a simple online tool designed for use by anyone with basic knowledge of the work area and process. There is no direct measurement of environmental conditions required to use the calculator.
The online calculator uses a number of factors to make a basic assessment of heat stress including:
Note: As the basic assessment is a qualitative assessment, instrumentation for measurement of wet bulb glove temperature (WBGT) is not mandatory meaning people with limited technical expertise and equipment can identify and assess the risk factors. The basic assessment can therefore be performed using readily available information at the workplace (i.e. ambient air temperature and relative humidity).
The online calculator is an initial qualitative review of potential heat stress situations and is not a definitive assessment tool.
A level 2 (technical) assessment will be needed when:
Level 2 (Technical): needs additional data collected and the use of a second level index such as ISO 7933: Predicted Heat Strain (PHS) or Thermal Work Limit (TWL). A range of measuring equipment and expertise is required for this type of assessment.
Additional data needed for this type of assessment will include:
This type of assessment and gathering of required data should only be undertaken by a competent person such as an occupational hygienist or occupational physician.
A level 3 (expert) assessment will be needed when either:
Level 3 (Expertise): Physiological monitoring
Physiological monitoring is used in cases of high heat stress risk such as:
The risk and severity of heat related illness will vary widely among workers, even under identical heat stress conditions. Individual monitoring measures a worker’s physiological responses (such as elevated body temperature and/or heart rate) to assess the effectiveness of implemented controls.