Dust monitoring on construction sites: PM10, PM2.5 and beyond

Dust monitoring on a construction site is the continuous measurement of airborne particulate matter at and around the site, used to control emissions in real time and to demonstrate compliance with environmental commitments. A well-designed programme measures the right particle sizes, uses methods suited to its purpose, places monitors upwind and downwind, and links alert levels to specific mitigation actions. Without those elements, data is difficult to act on and difficult to defend.

This article explains particle size fractions, measurement methods, network design, alerts and reporting.

Particle size fractions explained

Particulate matter is classified by aerodynamic diameter, measured in micrometres (µm).

Fraction	Definition	Typical construction sources	Why it matters
TSP	Total suspended particulate, all airborne particles	Earthworks, stockpiles, haul roads, demolition	Visible dust, deposition on property and vegetation, nuisance
PM10	Particles of 10 µm or less	Excavation, crushing, vehicle movement on unpaved surfaces	Inhalable into the upper airways, common regulatory parameter
PM2.5	Particles of 2.5 µm or less	Diesel engines, generators, cutting, fine fraction of earthworks	Penetrates deep into the lungs, closely linked to health effects
PM1	Particles of 1 µm or less	Combustion exhaust, welding fumes	Indicator of combustion sources, very fine fraction

The fractions are nested: PM1 is part of PM2.5, which is part of PM10, which is part of TSP. Construction activities generate mostly coarse particles, so PM10 and TSP usually respond most clearly to site activity, while PM2.5 and PM1 help identify combustion sources.

Choosing a measurement method

Real-time optical monitors

Optical monitors use light scattering to count and size particles, reporting concentrations at short intervals. Their advantages are immediate data, remote access, low maintenance and suitability for alarms. Their limitation is that readings depend on particle shape, density and humidity, so they are indicative unless corrected against a reference.

Reference and equivalent methods

Reference methods, typically gravimetric sampling onto filters that are weighed in a laboratory, and recognised equivalent methods such as beta attenuation monitors, provide data suited to formal comparison with standards. They are more expensive, need more maintenance, and gravimetric results are not available in real time.

A combined approach

A common and practical approach is to run optical monitors across the network for real-time control, and to co-locate at least one with a reference or equivalent method. This allows a site-specific correction to be applied to the optical data and strengthens the defensibility of the full data set. Confirm which methods are acceptable for compliance purposes on your project with the competent authority.

Designing the monitoring network

Upwind and downwind locations

Saudi Arabia experiences high natural background dust and regional dust events. Monitoring only downwind of the site cannot separate the site’s contribution from background. A defensible network includes:

• At least one upwind location representing incoming background
• Downwind locations at the site boundary facing sensitive receptors
• Additional locations near high-risk activities such as crushing, stockpiles and haul road exits
• A meteorological station recording wind speed and direction, temperature and humidity

Because wind direction changes, locations should be chosen from local wind data, and the upwind and downwind roles of each monitor assigned in the data analysis rather than fixed in advance.

Sensitive receptors

Identify receptors early: homes, schools, hospitals, offices, agricultural land and protected areas. Place boundary monitors on the line between major dust sources and the nearest receptors.

Practical siting

• Keep inlets clear of walls, trees and other obstructions
• Avoid locations directly beside a single dominant source unless that source is the target
• Provide secure power and communications, and protect equipment from damage and theft
• Document each location with coordinates, photographs and reasons for selection

Alert levels tied to mitigation

Alerts are only useful if they trigger action. A tiered approach links each level to a specific response:

Alert tier	Purpose	Example response
Advisory	Early warning of rising concentrations	Supervisor checks activities near the monitor, increases water spraying
Action	Concentrations approaching the project’s control level	Reduce or relocate high-dust activities, intensify suppression, review wind conditions
Stop	Concentrations at or above the control level and attributable to the site	Suspend the contributing activity until levels fall and causes are addressed

Set alert values according to the project’s environmental management plan, permit conditions and applicable air quality requirements, using averaging periods consistent with those requirements. Confirm current standards with the competent authority rather than relying on general figures. Each alert should notify a named person, and every response should be logged.

Reporting

Regular reports turn data into evidence. A useful monitoring report includes:

• Summary of results for each location and parameter against the project’s control levels
• Wind roses and analysis of upwind and downwind differences
• Record of alerts, investigations and mitigation actions taken
• Notes on regional dust events and data gaps, with reasons
• Calibration, maintenance and data validation records
• Recommendations for adjusting mitigation or the network

Setup checklist

• Monitoring objectives and parameters confirmed (PM10, PM2.5, PM1, TSP)
• Applicable requirements confirmed with the competent authority
• Sensitive receptors and main dust sources mapped
• Upwind, downwind and activity-focused locations selected using wind data
• Optical monitors co-located with a reference or equivalent method where needed
• Meteorological station installed
• Tiered alert levels defined, each with a mitigation response and owner
• Data validation, calibration and reporting procedures documented

How Selorin can help

Selorin’s dust monitoring service covers network design, installation of continuous monitors, alert configuration and periodic reporting, and links to our air quality monitoring and environmental management plans work. Agreeing the monitoring objectives and network layout before mobilisation is usually the most effective place to start.