WSH risk management: how to put heat stress into your risk assessment
Heat stress is a workplace hazard like any other, and MOM expects it in your risk assessment. Here is how to do it, step by step.
Under Singapore's Workplace Safety and Health (Risk Management) Regulations, employers, self-employed persons and principals must carry out risk assessments for the work they control. For outdoor work, heat stress is one of those risks, and it is the very first point on the MOM / WSH Council heat stress checklist.
Many sites already have a thorough risk assessment for working at height, lifting and machinery, but heat is missing or covered in one line. This guide shows how to add it properly.
What the law expects
The WSH Council and MOM describe risk management as a cycle:
- Prepare: form the team and list the work activities.
- Assess the risk: identify the hazards, then evaluate how likely and how severe harm would be.
- Control the risk: put measures in place to remove or reduce it.
- Keep records of the assessment.
- Review it.
You also need to communicate the risks and controls to workers, contractors and anyone else affected.
When to review
MOM's guidance is to review risk assessments at least once every 3 years, and sooner when:
- work processes or the site layout change significantly
- new machinery, substances or procedures are brought in
- someone is injured or an incident happens because of a hazard
- the assessment turns out to be inadequate
MOM's enhanced heat-stress measures taking effect on 1 December 2026 are a good reason to review the heat section now, even if the rest is recent.
Step 1: identify the heat hazard for each activity
Heat stress comes from three sources. Look at each one for every outdoor activity:
- Environment: WBGT level, direct sun, humidity, little airflow, heat from nearby plant or hot surfaces.
- Task: how physically heavy the work is, and for how long without a break.
- Worker: acclimatisation, age, health conditions, medication, and clothing or PPE that traps heat.
Step 2: evaluate the risk
Rate how likely heat illness is and how severe it could be. Heat stroke can be fatal, so severity is high for any heavy outdoor work. The likelihood depends on the WBGT band, the workload and the controls already in place.
Step 3: control the risk
Work down the hierarchy of controls, from most to least effective:
| Level | Example for heat stress |
|---|---|
| Eliminate | Move heavy work indoors or off-site where possible |
| Substitute | Use machinery for manual lifting during the hottest hours |
| Engineering | Shaded, ventilated rest areas, fans or air coolers, cool water stations |
| Administrative | Rest breaks by WBGT band, rescheduling to cooler hours, acclimatisation, buddy system, training, hourly WBGT checks |
| PPE and clothing | Loose, breathable workwear, cooling vests, while keeping the PPE the task requires |
MOM's heat-stress measures map neatly onto the engineering and administrative levels. Listing them in the risk assessment shows how each one controls the hazard.
A worked example
| Activity | Hazard | Risk before controls | Controls | Risk after |
|---|---|---|---|---|
| Rebar fixing on open deck, 8 am – 6 pm | Heat stress, heat stroke (high WBGT, heavy work, full sun) | High | Hourly WBGT check; rest 10 min/hour at WBGT 32°C and 15 min/hour at 33°C in a ventilated shelter; cool water within a 3 to 5 minute walk; 7-day acclimatisation; buddy system; heaviest lifting moved to before 11 am; emergency cooling kit on deck | Medium |
Name an owner for each control, for example "WSH officer: hourly WBGT log" or "site supervisor: water refills".
Step 4 and 5: record, communicate and review
- Keep the assessment on file with the date and who approved it.
- Brief workers in a language they understand, at toolbox talks and during heat-stress training.
- Set a reminder to review it, and review it straight away after any heat incident.
How HeatAware helps
The HeatAware kit covers the engineering and administrative controls in one package: rest shelter, water stations, WBGT monitoring, emergency cooling, and site documents you can attach to your risk assessment. The app keeps the WBGT log, alerts and training records that show the controls are working.
Size your kit and use the 17-point heat stress checklist to check the rest.
General guidance based on the WSH Council's About Risk Management and MOM's FAQ on reviewing risk assessments. For full requirements, see the WSH (Risk Management) Regulations and the Code of Practice on WSH Risk Management.