Interpreting Particle Sensor Readings Near a Construction Site

When building work starts nearby, particle sensor readings inside your home or building can change even if nothing has changed indoors. Dust from earthworks, demolition, cutting, sanding and truck movement can travel further than expected, then find its way in through open entries, gaps and ventilation paths.

The key is not just seeing a spike, but interpreting the pattern. Readings that rise and fall with site activity, wind direction and door use can point to infiltration or entrance leakage rather than an internal dust source.

What particle sensors can tell you

Particle sensors do not identify the exact dust source, but they can show changes in indoor particle concentration over time. That makes them useful for spotting patterns that line up with construction activity outside.

A few things matter when you are reading the data:

• •Baseline level: what the sensor shows when the building has been quiet for a while
• •Duration of peaks: brief bursts often suggest a one-off event, while longer elevation may indicate ongoing ingress
• •Time of day: readings that rise during working hours may track nearby site activity
• •Location in the building: a sensor near an entry, loading area or intake can read differently from one deeper inside the space

If you are using sensors in more than one room, compare them. A rise in one area only can suggest a local entry path, while several rooms climbing together may point to a broader infiltration issue or a ventilation pathway carrying dust through the building.

Patterns that often suggest construction dust infiltration

Construction dust usually enters a building through a combination of airflow, pressure differences and gaps in the envelope. The sensor pattern can offer clues about which pathway is most likely.

Short spikes after doors open

If readings jump when people enter or exit, and then settle again, dust may be getting in through the doorway or lobby. This is common where there is heavy foot traffic, shared access, or doors held open for deliveries.

Look for patterns such as:

• •a rise immediately after a door opens
• •higher readings during busy entry periods
• •readings that fall once the door is closed and the area is undisturbed

Gradual rise during site activity

A slower climb over the morning or afternoon can suggest outdoor dust is entering more steadily. This may happen when nearby cutting, excavation or sweeping stirs up fine particles that drift towards the building and are drawn inside through cracks, gaps or ventilation paths.

Higher readings near windows, gaps or service penetrations

If a sensor near a window, wall penetration, loading door or plant room reads higher than elsewhere, infiltration may be occurring at that point. Small gaps around frames, poorly sealed penetrations and unsealed service entries can all create weak spots.

Repeated peaks in windy conditions

Wind can carry dust across a site boundary and also increase the pressure differences that drive outdoor air indoors. If your readings rise on windy days, especially when the wind comes from the direction of the construction site, that is worth noting.

How to separate infiltration from an internal dust source

Not every particle rise is caused by the construction site. Internal sources can include cleaning, packaging, printers, renovations, cooking areas or movement of stored materials.

A useful way to separate the two is to compare sensor changes against what is happening both inside and outside.

Signs that point more towards outside air intrusion

• •the rise begins when nearby site activity starts
• •the increase happens even when indoor activity is low
• •several sensors near the perimeter rise before interior sensors do
• •the readings improve after doors and windows are kept closed
• •the issue is strongest when the wind is from the site side

Signs that point more towards an indoor source

• •the rise starts after cleaning, sweeping or equipment use inside
• •only one room shows a clear increase
• •the pattern repeats at the same indoor activity each day
• •the readings stay elevated even when the building is sealed as much as practical

If you are unsure, log the readings alongside notes on door use, weather, site noise and visible dust conditions. A simple record over a few days can make the pattern much easier to read.

What building managers and homeowners can check first

Before making changes to the filtration system, it is worth looking at the building itself. Small entry points can have a noticeable effect on dust intrusion.

Practical checks include:

• •inspect door seals and closers
• •check that loading docks and side entries shut properly
• •look for gaps around pipe, cable and duct penetrations
• •confirm windows are fully latched where they are meant to be closed
• •review whether air intakes are positioned near the dust source
• •check whether temporary works are changing normal airflow around the building

If the building has mechanical ventilation, the filter arrangement also matters. Under AS 1668.2:2024, ventilation design and site requirements should be confirmed with the mechanical services engineer or building owner. If you are unsure what is installed, review the equipment documentation or speak with the system designer before making changes.

Filtering and monitoring after the cause is identified

Once you know whether the dust is entering through the envelope or the ventilation path, you can choose a more targeted response. That might mean improving seals, changing how entries are managed, or reviewing the filter stage fitted to the system.

For air handling systems, the right filter depends on the equipment, the dust load and the site conditions. Some installations use coarse pre-filtration, while others use finer final filters where the system allows it. G3/G4/F5-F9 are EN 779 classes that are still commonly referenced in Australia, although ISO 16890 is now widely used. These rating systems do not convert directly, so it is best to match filters to the actual equipment and operating requirements rather than trying to compare labels across standards.

If a system uses HEPA filtration, the standard matters as well. Under EN 1822, H13 filters are at least 99.95% efficient and H14 filters are at least 99.995% efficient at the most penetrating particle size. That level of filtration is only appropriate where the system has been designed for it.

Useful checks include:

• •confirm the filter size and sealing arrangement before ordering replacements
• •monitor pressure drop where gauges are fitted
• •inspect more often when dust load increases or nearby works intensify
• •follow the filter and equipment manufacturer instructions
• •if a product is marked as washable, only wash it if the product instructions say it is designed for that purpose

If you need help matching a filter to an existing frame, start by measuring the filter correctly. Our guide on how to measure an air filter can help avoid ordering the wrong size.

When to bring in specialist support

If sensor readings stay elevated even after obvious entry points are managed, the issue may be broader than a single door or filter. That can mean the building pressure balance, intake placement or filtration setup needs review.

This is where a practical inspection helps. You may need to compare the sensor data with the ventilation layout, the current filter stage and the way the building is used during the day. For commercial sites, our commercial filter servicing and filter servicing pages explain the kinds of checks that can be done when a system needs attention.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, and we can help supply or make the right filters for the system you have. If you are trying to respond to dust from nearby construction, call 07 3800 3448 or request a quote.

You can also browse our products or custom air filters if you need a filter suited to a specific frame, size or application.