Heat Stress Management

Managing heat stress as Singapore gets warmer

2023 was Singapore’s fourth-hottest year1, with a sweltering high of 37°C in May 2023. In the Third National Climate Change Study2, Singapore’s climate is projected to become warmer, with very hot days becoming more frequent by the end of this century.

The rise in temperatures put workers, especially those working outdoors, at an increased risk of heat stress. For work to continue in a safe manner, employers will need to do more to protect outdoor workers.

In the upcoming months, the Ministry of Manpower will be conducting workplace inspections in the construction, shipyards and process industries, to check the effectiveness of heat stress measures for outdoor work.

Figure 1: Workers at a construction site working under direct sun.

Implementing an Effective Heat Stress Management Programme

To protect workers and increase resilience to rising temperatures, employers are required to implement enhanced heat stress measures for outdoor work3. Workplaces are to ensure effective implementation of the following protective measures: 

Figure 2: Example of a portable WBGT monitor.

Other Heat Stress Protective Measures

• Adequate ventilation: Cool rest and work areas with fans or air coolers.

• Light-coloured clothes: Provide breathable, loose-fitting and light-coloured clothing for outdoor workers to wear.

• Work rescheduling: Carry out physical work during cooler parts of the day.

• Mechanical assistance: Reduce physical exertion with mechanical aids, like manual handling equipment and powered tools.

Early recognition of signs and symptoms: Implement a buddy system to aid early recognition of heat-related signs, symptoms and illnesses (e.g. fainting spells, disoriented behaviours) for prompt interventions.

Heat-related illnesses may affect workplace safety or lead to a workplace accident. The WSH Council urges employers to partner workers and manage heat stress effectively, for a safe and healthy workplace.

1 The Straits Times (29 Jan 2024): 2023 was Singapore’s 4th hottest year, based on records kept from 1929 onwards.

2 Ministry of Sustainability and the Environment’s Joint Media Release on Singapore’s Third National Climate Change Study (5 Jan 2024).

3 Ministry of Manpower’s Press Release on Enhanced Measures to Reduce Heat Stress for Outdoor Workers (Oct 2023).

4 Workers who are vulnerable to heat stress includes those who are newly assigned to outdoor work; unacclimatised to working in hot environments (e.g. new or returning from countries with a cold climate); returning from long leave of more than a week; recovering from prolonged illness; and have personal factors (e.g. chronic diseases, medication use, history of heat injury or pregnant).

5 Refer to Page 17 of WSH Guidelines on Managing Heat Stress in the Workplace for an example of how to gradually increase a worker’s daily heat exposure.

For more information: 

Ministry of Manpower

Enhanced Heat Stress Measures for Outdoor Work

FAQs on Heat Stress Measures for Outdoor Work

National Environment Agency

Heat Stress Advisory

Workplace Safety and Health Institute

OWLinks Issue 79 – Heat Stress in the Workplace

Workplace Safety and Health Council

WSH Guidelines on Managing Heat Stress in the Workplace

Heat Stress Management Compliance Checklist

Specifications for WBGT Meters for Workplace Measurement

Monitor and Manage Heat Stress Poster

Heat Stress in the Workplace

Impact of Climate Change

Rising global temperature is increasing the risk of workplace heat injuries. From 1980 to 2020, the annual mean temperature in Singapore increased from 26.9°C to 28.0°C. The combined extremes of heat and humidity, decreased air movement or lack of shading from direct heat are harmful to human health and may lead to more occurrences of heat stress.

Heat stress occurs when the body is unable to cool down through perspiration. This causes the body temperature to rise rapidly, which may cause damage to the brain and other vital organs. Symptoms of heat stress include:

• Profuse sweating

• Inability to concentrate

• Dizziness

• Cessation of sweating

• Cool, moist skin with goose bumps when in the heat

• Severe thirst - a late symptom of heat stress

• Unconsciousness

Heat-related illness

Heat-related illnesses range from milder conditions such as heat rash, heat cramps and heat exhaustion, to more serious heat related illnesses such as heat stroke, which can be fatal or cause permanent disability if medical treatment is not administered promptly.

Studies indicated significant deterioration in mental functions, such as short-and long -term memory and visuospatial function, perceptive discrimination and reaction time in dehydrated subjects.5 Workers engaged in physical tasks were less productive and took longer to complete their tasks when given less water to drink. There was evidence from studies to indicate that dehydration could be linked to job-related accidents where dehydrated subjects fainted more quickly when subjected to an orthostatic challenge test (change in body posture).

Assessing risk factors for at-risk employees

Workers who are exposed to extreme heat or work in hot environments, for e.g. construction, boiler rooms, laundries, bakeries and kitchens may be at risk of heat stress. When there is a possibility of heat stress, conducting a risk assessment is a good starting point. Some factors (non-exhaustive), to consider include: 

If necessary, seek help from others who are more experienced in determining the risks from hot environments, for e.g. occupational hygienists or occupational health professionals.

Preventing heat stress at the workplace

In December 2020, the Workplace Safety and Health Council (WSHC) published a revised comprehensive guideline on managing heat stress in the workplace (first published in 2010).4 The guideline can be downloaded here

Preventive measures can be taken to limit a worker’s exposure to heat, which could raise the ability of the worker to cope with the heat. These include assessing fitness-to work, work scheduling, adequate water intake and worker awareness

Additional preventive actions for hot indoor working environments include insulation and shielding from hot surfaces, ventilation and air conditioning as well as reducing ambient humidity

And here is the Heat Stress Management Compliance Checklist

Ice slurry

There are many studies to show that ingesting ice slurry mitigates heat injuries and improves heat tolerance, by lowering body core temperature by about half degree Celsius. Ingestion of ice slurry is also shown to be more efficient than drinking cold water.

A serving of 200-400ml of ice slurry would cool the body and improve heat tolerance for up to an hour, after which the effects will start to wear off. It is recommended to consume the ice slurry just before high intensity exercises, such as a 10km run.

The science of ice slurry is proven in sports and there are potential use cases for other industries such as construction, marine and healthcare. Using ice slurry to mitigate heat stress is also one of the recommended measures under WSH Guidelines ,with the added advantage of being a pre-emptive solution rather than a reactive one

Heat Stress Management

Heat Stress at Work 

Working in Singapore’s hot and humid weather can put you at an increased risk of heat stress.

Heat stress occurs when the body is unable to remove excess body heat, and this excess accumulated heat then harms the body.

Heat stress related illnesses include heat cramps, heat exhaustion and heat stroke, with heat stroke being potentially fatal.

Preventing Heat Stress

Heat stress must not be overlooked, and you should take the necessary measures to protect yourself from heat-related risks.

Prevention Tips:

Do not over-exert yourself in the first two weeks of work, especially if you have just arrived from a cooler country.

• Acclimatise yourself to the hot weather.
• Wear loose-fitting and light-coloured clothes when outdoors.
• Work under the shade where possible.
• Drink lots of water – at least 500ml (one bottle) every hour.
• Take regular breaks in cool shaded areas.
• Sponge yourself with water during breaks or meals.
• Adopt a healthy lifestyle with proper meals and sleep.

Helping Someone with Heat Stroke

If you notice someone with signs of heat stroke, call 995 for an ambulance immediately. While waiting for the ambulance, you should:

• Move the person to a shady or cooler area;
• Loosen or remove the person’s clothing;
• Apply cool water and fan on the person; and
• Place ice packs under the person’s armpits and groin area.

For more information

Check out WSH Guidelines on Heat Stress Management.

Check out ABC Checklist -Working Safely in Hot Environment