Prevention of Heat Stroke

Supply Cool Drinking Water

• Drink 250 to 500 ml of water or other appropriate beverages per hour to replenish fluids and electrolytes lost through sweating

Reduce Heat Absorption

• Set up shades or covers to block sunlight or isolate heat sources
• Use sun protection equipment, such as wide-brimmed hats, neck shades and sun protection sleeves, to avoid exposure to direct sunlight
• Wear loose-fitting clothing to enhance sweat evaporation, ensuring garments are not so loose that they risk entanglement in moving machine parts

Increase Heat Dissipation

• Wear light-coloured and air-permeable clothing, and use cooling towels
• Use blowers, misting fans, or portable fans to enhance ventilation

Reduce Physical Exertion

• Use suitable mechanical aids to minimize physical exertion
• Reduce workload and pacing
• Arrange job rotations alternating between hot and cool locations

Arrange Working Hours

• Schedule outdoor and physically demanding work during cooler daytime periods, such as before 10 a.m. or after 4 p.m.

Arrange Rest Time and Place

• Rest in shaded areas with good ventilation
• Implement basic rest breaks based on workload intensities:
  • Light to Moderate workloads: Take a 10-minute break after every 2 hours of work
  • Heavy to Very Heavy workloads: Take a 15-minute break after every 2 hours of work
• Provide additional rest time whenever the Heat Stress at Work Warning is in effect

Staff and students should be aware of the signs and symptoms of heat-related illness so they can identify issues early and take appropriate responses immediately.

Common early signs and symptoms of heat-related illness:

When core body temperature reaches 41°C or higher, the individual may experience convulsions or become unconscious. This is a medical emergency indicating heat stroke. Body temperature must be brought down immediately and first aid administered, otherwise the life of the individual is in grave danger.

If any of the aforementioned signs and symptoms appear, seek emergency help as soon as possible, move the affected person to a cool environment and provide appropriate first aid treatment according to condition.

When situated in a hot environment, the human body increases blood flow to the skin and perspires to dissipate heat. If environmental temperature is too high or a large amount of heat is generated by physical work, the body's physiological regulating mechanism may fail to control core temperature effectively. This increases heat stress and leads to a higher risk of heat stroke.

Various risk factors, including temperature, humidity, heat radiation, air flow, workload, work clothing, personal health status and adaptation to working in a hot environment, should be considered when carrying out a heat stress risk assessment. The evaluation should comprehensively cover environmental factors, work factors and person factors. HS Form 32 is available to facilitate this heat stress risk assessment.

The Labour Department (LD) issued the Guidance Notes on Prevention of Heat Stroke at Work. The guidelines state that appropriate rest arrangements are necessary for outdoor work during times of Heat Stress at Work Warning. The length of rest depends on physical workload and the specific level of the warning.

For comprehensive regulatory criteria, please refer to the following official resources: 

• Physical Workload Categories and Examples (Appendix 1 of Guidance Notes on Prevention of Heat Stroke at Work)

• Rest Arrangements for Outdoor Work in Times of Heat Stress at Work Warning (Appendix 4 of Guidance Notes on Prevention of Heat Stroke at Work)

*Please note that the statutory charts show baseline rest arrangements for an individual working outdoors without any implemented heat stress preventive measures.

Several environmental and operational factors allow for adjustments to the baseline hourly rest time:

• Reductions in rest time (subtract 15 or 30 minutes):
  Working in an indoor environment, providing shading facilities (such as a shelter or sun-blocking cover) or utilizing devices that facilitate heat dissipation (such as blowers, misting fans, portable fans, or cooling vests containing frozen packs or refrigerating devices) can reduce mandatory hourly rest time by 15 minutes per measure. Providing both shelter and effective mechanical ventilation such as blowers simultaneously can reduce hourly rest time by 30 minutes.
• Increases in rest time
  Conversely, working in a location with poor ventilation, wearing non-breathable protective clothing, or being exposed to a heat source without effective heat shielding increases heat stress. Additional hourly rest time should be added to the baseline requirement under these conditions.

At PolyU, tasks involving maintenance, gardening, cleansing, security, and event organizing pose a risk of heat stress. According to the regulatory guidelines, these tasks are categorized as either low or moderate workloads.

Practical Application Example: Under the Red Heat Stress at Work Warning, a baseline moderate workload requires 30 minutes of rest per hour. If a maintenance worker is working outdoors with a portable fan, the required hourly rest time drops from 30 minutes to 15 minutes.