The skyline goes soft first. By mid morning the far tower cranes are grey outlines, the smell of burning has settled into everyone’s overalls, and somebody asks the supervisor whether they are still pouring this afternoon.

Haze arrives without a siren, and that is the difficulty. There is no single moment where work obviously has to stop, so sites tend to carry on as normal until someone starts coughing. A plan decided in advance takes that judgement out of the middle of a shift.

Read the index, not the sky

Air quality is reported by the National Environment Agency (NEA) as the Pollutant Standards Index (PSI), computed from the 24 hour average concentration of six pollutants, among them fine particulate matter known as PM2.5. Because that figure is a rolling average, it lags behind what the air is doing right now. NEA also publishes 1 hour PM2.5 readings, which respond faster and are the better guide when conditions are changing during a shift.

Visibility is a poor substitute for either. Humidity, time of day, and the angle of the sun all change how thick the air looks without changing what is in it, so a site that decides by eye will be wrong in both directions. Assign the reading to someone, at a set time, from the NEA air quality information rather than from a group chat.

What the PSI bands ask of employers

MOM’s guidelines on protecting employees from haze set out what employers should do as readings climb. The bands below summarise the guidance for healthy employees doing outdoor work, and the guidance is updated periodically, so check the current version before writing it into a site procedure.

Masks are the last control, not the first

Personal protective equipment (PPE) sits at the bottom of the hierarchy of controls for good reason. Before reaching for masks, look at what can be removed from the open air altogether: prefabrication moved under cover, cutting and grinding relocated indoors, non urgent external works pushed to a clearer week, and plant fitted with enclosed cabs used in place of hand work where that option exists.

Where outdoor work has to continue, rotation does more than most people expect. Shorter spells outside, longer recovery indoors or in a shaded rest area with clean air, and the heaviest tasks moved to whichever part of the day is reading lower will all cut total exposure without stopping the job. This kind of planning belongs alongside the hazard control thinking taught in construction safety courses, where the point is always to control the exposure before protecting the person.

When masks are used, fit is the whole story. A respirator that seals badly offers a fraction of its rated protection, and facial hair, damaged straps, and the wrong size all break the seal. Anyone expected to wear one for prolonged strenuous work should be shown how to check the seal, and given a replacement when it becomes damp, soiled, or damaged.

Some workers need more protection

MOM’s guidance draws a clear line between healthy employees and those who are elderly, pregnant, or living with a chronic heart or lung condition. Those employees are advised to minimise prolonged or strenuous outdoor work once the 24 hour PSI passes 100, and to avoid outdoor work as levels climb further. This depends entirely on employees feeling able to declare a condition without it counting against them, which is a matter of how the site is run rather than what the policy says.

Haze on top of heat

Haze rarely arrives on a cool day. Dry weather brings both, and the two problems compound: workers breathe harder in poor air, take fluids less readily while wearing a mask, and tire faster than the same task would normally cost them.

Watch for the signs of heat injury alongside the respiratory symptoms, because a worker who has stopped sweating and becomes confused needs a very different response from one who is short of breath. Keep water within reach of the work face instead of at the site office, and make rest breaks a scheduled instruction instead of something a worker has to ask for.

Briefing the crew so the plan works

A haze plan that lives in a folder will not change what happens at two in the afternoon. Put it into the toolbox talk on the first hazy morning, and keep it short enough that everyone remembers it:

• Who checks the readings, at what times, and where the crew can see the result
• What changes at each band, in terms of specific tasks on this site
• Where masks are kept, who fits them, and how to get a replacement
• Which symptoms mean stopping work and telling the supervisor immediately
• Who has authority to halt an activity without waiting for approval

Conclusion

Haze is a hazard that can be forecast, measured, and planned around, which puts it in a better position than most of what a site deals with. The difference between a well handled haze week and a bad one is almost always whether the decisions were made in advance or improvised at the point when someone was already struggling.

Write the thresholds into the site procedure while the air is clear, name the person who reads them, and agree which activities move under cover at each band. Those three decisions take an afternoon, and they remove almost all of the argument that otherwise happens at the worst possible moment.

Wong Fong Academy has trained site teams across Singapore since 2011, and our sessions deal with the conditions our learners actually work in, from tropical heat to poor air days. Sign up for training and give your supervisors the grounding to make those calls early.

‍