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Prevention of Heat Stroke


The hot and humid summer in Hong Kong poses an increased risk of heat stroke to people working in both indoor and outdoor areas in which air conditioning systems are lacking. In addition, people who are required to work near heat sources or heat-generating facilities are also at risk of heat stroke.

Prevention of heat stroke is crucial to protecting our students and staff who are involved in hot environments.  To prevent people from getting heat stroke, risk assessment on heat stress shall be conducted and based on the assessment results, appropriate measures will be taken. Heat stress risk factors include environmental factors (e.g. ambient temperature, relative humidity, heat radiation and air flow), work factors (e.g. physical workload, duration, personal protective equipment and clothing) and personal factors.

HSO aims to give health and safety advice on control measures to prevent heat stroke and advise on heat stress risk assessment issues that may affect PolyU students, staff and visitors. The goal is to reduce the risk of heat stroke.

Supply Cool Drinking Water

  • Take plenty of water or other appropriate beverages to replenish the fluid and electrolytes lost during sweating
  • Drink approximately 250 – 500 ml of water or other appropriate beverages per hour

Reduce Heat Absorption

  • Set up shade or cover for blocking sunlight / isolate heat sources
  • Use sun protection equipment (wide-brimmed hats, neck shades, sun protection sleeves) to avoid exposure to direct sunlight
  • Wear loose-fitting clothing to enhance sweat evaporation. Be aware that clothes which are too loose may get entangled in the moving parts of machines

Increase Heat Dissipation

  • Wear light-coloured and air permeable clothing and use cooling towel
  • Use blowers/ misting fans/ portable fans to enhance ventilation

Reduce Physical Exertion

  • Use suitable mechanical aids to minimize physical exertion
  • Reduce loading and pace of work
  • Arrange job rotation in hot and cool locations alternately

Arrange Working Hours

  • Schedule outdoor and physically demanding work to cooler daytime periods (e.g. before 10 a.m. or after 4 p.m.)

Arrange Rest Time and Place

  • Rest in shaded areas with good ventilation
  • Basic rest time:
    • Light to Moderate workloads: 10 minutes rest break after every 2 hours of work
    • Heavy to Very Heavy workloads: 15-minute rest break after every 2 hours of work
  • Provide more rest time, when Heat Stress at Work Warning is in effect

Students and staff should be aware of the sign and symptoms of heat-related illness so that they could identify related symptoms early and take appropriate responses immediately.

Common early signs and symptoms of heat-related illness:



Overall appearance:
Nausea or vomiting
Fatigue and weakness

Overall feeling:
Nausea (feel like vomiting)

Reaction and conscious level:

Reaction and conscious level:

Rapid and shallow breathing

Rapid breathing
Breathing difficulty

Blood circulation:
Rapid and weakening pulse

Blood circulation:

Other symptoms:
Muscle cramp (especially in feet and abdomen)

  • Clammy skin, excessive sweating, and pale (common in heat exhaustion)
  • Dry skin, flushing, fever and without sweating (common in heat stroke)

Other feelings:
Cramps and pain in the arms, legs and abdomen
Increase in body temperature

When the body temperature reaches 41°C or higher, the sufferer will have convulsion or become unconscious; and this is heat stroke. Immediately, the body temperature must be brought down and first aid should be given, or else the life of the sufferer will be in great danger.

If the aforementioned signs and symptoms appear, seek help as soon as possible, cool down the affected person, and provide appropriate first aid treatment according to his/ her condition.

When situated in a hot environment, the body will increase blood flow to the skin and perspire to dissipate heat. If the temperature of the environment is too high or a large amount of heat is generated by physical work, and the body's physiological regulating mechanism fails to control body temperature effectively, this will increase heat stress and lead to a higher risk of heat stroke.

Various risk factors, including temperature, humidity, heat radiation, air flow, workload, work clothing, one’s health status, and his/ her adaptation to working in a hot environment should be considered when carrying out risk assessment of heat stress. The risk assessment should cover the environmental factors, work factors and person factors. HS Form 32 is available to facilitate the heat stress risk assessment.

The Labour department of HKSAR issued a guidance note on the prevention 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 the physical workload and the level of Heat Stress at Work Warning. For details, please refer to the following hyperlink on Physical Workload Categories with Examples and Rest Arrangements.

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 chart shows the rest arrangement for a person working outdoors without any preventive measures on heat stress.

Several factors which can affect heat stress are related to adjustments to the rest time. Working in an indoor environment or providing shading facilities (such as a shelter or sun-blocking cover) and devices to facilitate heat dissipation (such as blowers, misting fans, portable fans, or cooling vests containing frozen packs or refrigerating devices) can reduce hourly rest time by 15 minutes each. Additionally, providing both shelter and ventilation such as using blowers simultaneously, can reduce hourly rest time by 30 minutes. Conversely, conditions such as working in a location with poor ventilation, wearing non-breathable protective clothing, or being exposed to a heat source without effective heat shielding increase heat stress, and additional hourly rest time should be added.

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

For example, under the red heat stress at work warning, a maintenance worker working outdoors with a portable fan will need 15 minutes of hourly rest time as the provision of the fan could reduce the hourly rest time from 30 minutes to 15 minutes.


Senior Health and Safety Manager
Mr CHEUNG Chi-yeung Alex


Health and Safety Manager
Ms YU Hoi-yan Karen

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