Outdoor Work During Haze: What Supervisors Should Decide Before PSI Spikes

Haze in Singapore is often discussed as a public health advisory. For workplaces, especially those with outdoor or strenuous tasks, it is also an occupational health and operational safety risk.

The practical question is not only, "What is the PSI today?" It is also: who is working outdoors, how strenuous is the task, how long will exposure last, are workers vulnerable, is visibility affected, and what should supervisors change before conditions worsen?

For employers, occupiers, principals and contractors, haze planning should not be a mask-buying exercise. It should be a clear trigger system that helps supervisors make timely work decisions.

Why Haze Matters At Work

MOM's haze guidance for employers says prolonged or strenuous outdoor work should be reduced, minimised or avoided depending on air quality. MOM also says risk assessments should consider haze effects, individual health and working conditions, with controls such as mechanical aids, job rotation, indoor rest breaks, hydration, symptom reporting and deferment of non-essential work.

MOH's haze advisory explains that health impact depends on a person's health status, PSI level, and the duration and intensity of outdoor activity. PSI 101 and above is considered unhealthy.

That matters for work such as:

• Construction, lifting, roofing, facade work, earthworks and manual handling.
• Landscaping, cleaning, pest control, security, facilities and maintenance work.
• Logistics, transport, loading bay, port, yard and delivery operations.
• Outdoor contractor work that continues because of schedule pressure.
• Visibility-sensitive tasks involving vehicles, cranes, traffic control or work at height.

Haze also interacts with heat stress and fatigue. Masks and respirators can increase breathing effort during physical work, so issuing N95 masks without adjusting work pace, rest breaks and task planning is not enough.

What Organisations Should Know

24-hour PSI and 1-hour PM2.5 serve different decisions. NEA explains through its air pollution FAQs that 24-hour PSI is used for health advisories and planning, while 1-hour PM2.5 readings help interpret current short-term air quality during haze episodes. Workplaces should use both: PSI for shift planning, and 1-hour PM2.5 for immediate supervisor decisions.

There is no single universal stop-work PSI for every outdoor job. Singapore guidance is risk-based. A short low-intensity outdoor task is different from several hours of strenuous lifting, crane signalling or road work.

Haze belongs in the risk assessment. MOM's risk management guidance expects workplace safety and health hazards to be identified, evaluated, controlled, monitored and communicated. WSH Council risk assessment guidance also recognises outdoor work during adverse environmental conditions such as haze as a risk that may affect respiratory health.

Respiratory protection is a programme, not a carton of masks. Where masks or respirators are needed, employers should consider fit, training, medical fitness, replacement, compatibility with other personal protective equipment, breathing effort and heat strain.

Contractors need the same triggers as employees. If an occupier or principal allows contractor work to continue outdoors, the haze controls should be coordinated. Site rules, rest locations, reporting lines and stop-or-defer authority should be clear before workers are deployed.

Common Gaps We See

• Waiting too long to decide. If the first discussion happens only when PSI spikes, supervisors may already have workers outdoors with no agreed plan.
• Treating all outdoor work the same. Prolonged, strenuous and visibility-sensitive work need different controls from ordinary movement between buildings.
• Using masks as the main answer. Masks may help in some conditions, but they can also increase breathing effort and discomfort during physical work.
• Ignoring vulnerable workers. Workers with chronic heart or lung disease, older workers, pregnant workers and symptomatic workers may need reassignment or additional protection.
• Forgetting visibility. Haze can affect crane work, vehicle movement, traffic control, banksman duties, work at height and emergency response.
• Leaving contractors to manage separately. On shared worksites, inconsistent haze triggers can create confusion and pressure to continue unsuitable outdoor work.

Practical Steps To Consider

1. Add haze into risk assessments and safe work procedures for outdoor, prolonged, strenuous and visibility-sensitive tasks.
2. Create a PSI and PM2.5 trigger matrix that tells supervisors when to reduce, minimise, avoid, defer or escalate work.
3. List essential and non-essential outdoor work before haze season. Do not debate this during the shift.
4. Assign monitoring responsibility. Decide who checks Haze.gov.sg, NEA/MOH advisories, current 1-hour PM2.5 readings and site visibility.
5. Plan clean-air rest arrangements such as indoor rest areas, hydration points and controlled breaks.
6. Use upstream controls first. Defer work, move work indoors, mechanise manual tasks, rotate workers and shorten exposure before relying on personal protective equipment.
7. Manage respiratory protection properly where required, including fit testing, training, stock, replacement and medical fitness considerations.
8. Brief contractors and supervisors together. Everyone on site should understand the same haze triggers and escalation rules.
9. Record decisions during haze episodes, especially when outdoor work continues under unhealthy, very unhealthy or hazardous conditions.

A Simple Supervisor Test

Before outdoor work starts, supervisors should be able to answer:

• Is the task prolonged, strenuous, visibility-sensitive or non-essential?
• What are the current 24-hour PSI and 1-hour PM2.5 conditions?
• Which workers should avoid or reduce exposure?
• Where will workers take indoor rest breaks?
• What changes are required if haze worsens during the shift?
• Who can approve deferment, redeployment or stoppage?
• Are contractors following the same instructions?

If those answers are unclear, the haze plan is not ready enough.

How DASH Consult Can Help

DASH Consult supports organisations with workplace safety and health risk assessments, occupational health controls, contractor safety management, adverse weather planning, respiratory protection programme review and practical supervisor-ready procedures.

For haze-related work, we help companies translate MOM, MOH, NEA and WSH expectations into usable site controls: trigger matrices, toolbox briefing content, contractor requirements, rest and hydration arrangements, and decision records.

FAQ

Must all outdoor work stop at a specific PSI level?

Singapore guidance is risk-based. MOM and MOH guidance focuses on reducing, minimising or avoiding prolonged and strenuous outdoor work depending on air quality, health status, duration and intensity. Employers should create task-based triggers instead of waiting for one universal stop-work number.

Should workplaces use PSI or 1-hour PM2.5?

Use both. The 24-hour PSI supports health advisories and next-day planning. The 1-hour PM2.5 reading helps supervisors respond to current short-term conditions during a shift.

Are N95 masks enough for haze work?

Not by themselves. Respiratory protection must be selected, fitted, trained, maintained and supervised properly. Employers should also consider breathing effort, heat strain, worker health, rest breaks and whether the work should be deferred instead.

Where can employers check Singapore haze guidance?

Key public sources include MOM's haze guidelines for employers, MOH's haze advisory, NEA and Haze.gov.sg readings, MOM's risk management guidance, and WSH Council risk assessment guidance.