Physiological monitoring

Physiological monitoring should be used when all other alternatives cannot be implemented either on grounds of practicality or because employees are working in environments outside the design parameters of a heat stress index eg WBGT. 

When performing physiological monitoring you are advised to seek specialist help and use the standard ISO 9886.

These measurements (eg core temperature, heart rate, sweat rate etc) require:

• Employees give their informed consent ie they are fully aware of any discomfort or risks associated with the measurement technique to be used and that they agree to their use and their own participation. 
• Employees are able to withdraw from these measurements at any time.  This ensures that the monitoring is ethical ie the physiological measurements being taken do not expose an individual to unacceptable risks due to the measurements being taken. 

It may be that the only way to ensure that workers are not being put at risk from heat stress is for personal monitoring procedures of the workers to be implemented.  Due to practical limitations this is usually done periodically, although this reduces the rate of risk of detection.

The following needs to be considered:

• The measured site must be valid and appropriate for the environment and the job;
• Non-contact infrared tympanic temperature is NOT to be used for measuring deep internal body temperature;
• There are two reasons for monitoring:
  • Post exposure evaluation of minute by minute data;
  • Real-time exposure monitoring of workers;
• The former provides a basis for establishing work/rest schedules.  The latter would be for continuous health monitoring during the exposure; 
• If the latter is to be used as part of a safety procedure during exposure to extreme environments, there is a need for those responsible for health and safety to have instant real-time access to data during the entry.  Therefore there is a need for this information to be transferred electronically from worker to health and safety monitor;
• It is recommended that where reasonably possible, real-time data be observed so that the physiological performance of staff can be monitored, and where limits are exceeded withdrawal protocols implemented;
• The interpretation of the results of physiological monitoring requires training and only personnel that are adequately trained and competent should interpret this data.
• The standard ISO 9886 and the information contained in the Tools and Risk Assessment enables a decision to be made on which method to use.
• Devices that sound alarms when limiting criteria are reached may provide a control methodology if the equipment used is calibrated and has been shown to provide a valid reading.  The validity of such equipment should be established prior to use in industrial settings. 
• All measuring equipment, transmission equipment, recording and data logging equipment should all undergo regular calibration checks by authorised calibration laboratories. 
• Careful consideration should also be made of the implications of such devices or systems ensuring that they will not reduce the ability for rapid evacuation of the wearer from the environment in which they are operating, and that system failures will not increase the risk.
• Other considerations such as evacuation time, emergency evacuation procedures etc. should also be considered.

There is no current standard describing the specification for physiological monitoring equipment.

Discontinue work and remove worker from the environment and protective clothing if:

• If core temperature limits exceed 38°C for unacclimatised workers or 38.5°C for acclimatised workers.
• Workers complain of any of the symptoms of heat related illness. 
• The taking of core temperature and skin temperature requires specialist equipment and training.  Unless the appropriate equipment and appropriate trained personnel are available these measures should not be undertaken.           

• Heart rate

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