Why it matters

Your body makes heat when you work. In Singapore's heat and humidity, sweat dries slowly and the body cannot shed that heat. Core temperature rises. First the worker feels tired and dizzy. Then they make mistakes. Heat stroke can kill within hours.

Heat also raises other risks. A dizzy worker on a ladder or a tired crane operator is a hazard to everyone nearby.

What raises the risk

The WSH Council heat stress guidelines group the causes into the environment and the work itself.

  • Environment: high air temperature, high humidity, still air, direct sun, hot engines and hot surfaces.
  • Work: heavy physical tasks, and clothing or PPE that traps heat, such as coveralls or chemical suits.
  • Person: MOM lists workers over 65, pregnant workers, obese workers and anyone new to outdoor work as more at risk. It adds workers back from more than a week's leave, those who are unwell, and those with chronic disease, certain medicines or past heat illness.

Measure the heat: WBGT

Air temperature alone misses humidity, sun and wind. The Wet Bulb Globe Temperature (WBGT) combines all four. MOM's outdoor heat framework sets three bands: below 31°C, 31°C to under 33°C, and 33°C and above.

Take a reading every hour during work, more so in the hottest part of the day. Write each reading down and tell the crew which band they are in. Act on the band straight away.

MOM's framework covers outdoor work. Hot indoor areas need the same thinking. Boiler rooms, kitchens, ship holds and areas near furnaces can be hotter than the open site. The WSH Council guidelines apply to both.

Order of controls

Plan the work around the heat first. Water and rest come after that.

  • Reschedule: move heavy outdoor work to the cooler hours. Avoid direct sun from about 11am to 3pm where you can.
  • Engineering: shade over work areas, fans or air coolers, insulation or shields on hot equipment, mechanical aids to cut physical effort.
  • Administrative: acclimatisation, job rotation, hourly water, shaded rest breaks, a buddy system.
  • Clothing: loose, light-coloured work wear. Allow extra breaks when workers must wear heavy PPE.
Check urine colour

Put a urine colour chart in the site toilets. Pale yellow means good hydration. Dark yellow means drink now.

Acclimatisation

A body takes about a week to adapt to heat. Until then a fit young worker can collapse doing work the rest of the crew handles fine.

The WSH Council gives a sample plan. Start with two hours of heat exposure on each of the first two days. Give light, shaded work for the rest of the day. Add one hour a day after that. Keep new workers out of the midday sun for the first two days. Repeat a shorter version for anyone back from leave or illness.

What the rules require

The WSH Act makes employers and occupiers protect workers' health. MOM's heat stress measures for outdoor work set out what it expects. MOM marks these as requirements:

  • Monitor WBGT every hour during work hours.
  • Use an on-site WBGT meter at construction sites with a contract sum of $5 million or more, shipyards and process plants. Other workplaces may use NEA's myENV app.
  • Acclimatise new workers and those back from more than a week's leave over at least 7 days.
  • Workers must drink regularly. At WBGT 31°C and above, they must drink at least every hour. MOM recommends 300 ml an hour or more.
  • Give adequate rest under shade. At WBGT 32°C and above, heavy physical work needs a break of at least 10 minutes every hour.
  • Have an emergency response plan and a reporting procedure.
From 1 December 2026

MOM will make four current recommendations mandatory. You will need heat stress training for exposed workers and cool drinking water near work areas. You will also need cold water, ice packs or water spray on standby, and suitable clothing against heat. Source: MOM.

Spot heat illness and act

Teach every worker the signs. Pair them up so each person watches a buddy.

Early signs are heavy sweating, thirst, headache, dizziness, cramps and nausea. Stop the worker. Move them to shade. Loosen clothing, give water and let them rest. Do not send them back until they feel well.

Heat stroke is an emergency. Watch for confusion, slurred speech, odd behaviour, fits or collapse. The skin may be hot. Some heat stroke victims still sweat. Call 995. Start cooling at once with cold water, ice packs and fanning. Keep cooling until help arrives. Never leave the worker alone.

Confusion is the key sign

A worker who is confused or acting strangely in the heat has heat stroke until proven otherwise. Do not let them walk off to rest alone.

Common mistakes

These come up again and again in heat incidents.

  • Putting new arrivals on full shifts in the sun from day one.
  • Taking a WBGT reading in the morning and not again.
  • Water stored far from the work area, or left in the sun.
  • Rest areas with no real shade, or seating on hot metal.
  • Letting a dizzy worker rest alone where no one can see them.
  • Treating heavy PPE work the same as light work in the heat.

Use it on site: the heat stress checklist and the toolbox talk to brief your crew.

Sources

  1. Heat stress measures for outdoor work, Ministry of Manpower.
  2. WSH Guidelines on Managing Heat Stress in the Workplace, WSH Council.

This is practical guidance, not legal advice. Laws and codes of practice change; always check the current official text and your site's own procedures.