The smallest threats are often the hardest to see…
Air pollution isn’t just about smoggy city skylines or visible dust clouds. Some of the most harmful and disruptive airborne contaminants are microscopic, so small they can pass straight through the human respiratory system or infiltrate sensitive manufacturing environments undetected.
For facility managers, engineers, and environmental professionals, understanding the size, nature, and concentration of airborne particles is the foundation of effective air filtration. The science of clean air begins at the microscopic level, where dust becomes data.
What is a Particle, and Why Does it Matter?
A “particle” is any solid or liquid matter suspended in air. These particles can vary dramatically in size, composition, and behaviour. Large particles, such as coarse dust or lint, settle quickly under gravity. Fine particles, however, can stay suspended in the air for long periods, moving through ventilation systems and into occupied spaces.
The size of these particles, measured in micrometres (µm), directly affects how they interact with filters, the human body, and the environment. For example:
- A grain of sand measures about 90 µm in diameter.
- Pollen averages 30 µm.
- Typical household dust is around 10 µm.
- Combustion smoke and bacteria fall between 0.3 and 1 µm.
- Viruses and submicron aerosols can be smaller than 0.1 µm.
At this scale, a single cubic metre of air can contain millions to hundreds of millions of particles, depending on location, activity, and air quality controls in place.
Particle Size and Human Health
From a health standpoint, particle size is critical. Larger particles are often trapped by the nose and throat, but smaller ones penetrate deeper into the respiratory tract.
Particles smaller than 10 µm (PM₁₀) can reach the upper airways, while those under 2.5 µm (PM₂.₅) can enter the alveoli; the tiny sacs in the lungs where oxygen is exchanged with the bloodstream. Once there, these particles can trigger inflammation, contribute to chronic respiratory disease, and carry harmful chemicals or microorganisms into the body.
In Australia, exposure to fine particulate matter is regulated by the National Environment Protection (Ambient Air Quality) Measure (NEPM), which limits average PM₂.₅ and PM₁₀ concentrations in outdoor air. However, indoor environments, especially industrial facilities, often experience far higher concentrations without filtration.
Clean air standards in the workplace are not just about comfort; they are an essential part of occupational health and safety.
How Particles Behave in the Air
Particles don’t all move the same way. Their size, shape, and density influence how long they remain suspended and how easily they are captured by filters. Larger, heavier particles settle quickly due to gravity, while smaller ones follow air currents, diffuse randomly, or remain airborne indefinitely.
In HVAC systems, particle behaviour determines how contaminants spread. Fine particles can travel long distances through ductwork, settle on surfaces, or bypass poorly maintained filters altogether. The smaller the particle, the greater the challenge for air filtration, which is why filter design and testing must account for particle size distribution.
Measuring Air Quality: From Visual Dust to Micron Precision
The earliest methods of assessing air cleanliness relied on visual cues; how “dirty” the air looked or how much dust accumulated on surfaces. Today, air quality measurement is data-driven, using precise instruments to count and categorise particles.
Modern testing technologies include:
- Optical particle counters, which measure the number and size of airborne particles in real time.
- Gravimetric analysis, which measures the mass of collected dust over time.
- Photometric and opacity methods, which estimate concentration based on light scattering.
These tools form the foundation for filter performance testing under standards like AS 1324.2 and AS 4260, ensuring that filtration products meet defined efficiency thresholds.
AES Environmental’s NATA-accredited testing facilities use such technologies to validate the performance of air filters, verifying not only particle capture efficiency but also resistance, dust-holding capacity, and airflow performance.
How Filter Efficiency is Determined
Every air filter has a performance curve, which indicates how efficiently it removes particles of different sizes. The most critical size range is known as the Most Penetrating Particle Size (MPPS) which is typically around 0.1 to 0.3 µm.
At this scale, neither inertial impaction nor diffusion dominates, making it the hardest size range to capture. That’s why HEPA filters are tested at 0.3 µm. If they can effectively remove particles that small, they will perform even better with both larger and smaller ones.
Filtration mechanisms vary depending on filter design:
- Inertial impaction captures larger particles as air changes direction through fibres.
- Interception traps mid-sized particles as they follow airflow paths.
- Diffusion captures the smallest particles as they move randomly and collide with fibres.
Together, these mechanisms ensure that well-designed filters remove nearly all airborne contaminants, even those invisible to the eye.
Why Particle Data Matters for Industry
Understanding particle size isn’t just academic. It has practical implications for every sector AES Environmental serves.
In pharmaceutical manufacturing, even a single submicron particle can compromise sterile environments or contaminate product batches. In electronics, airborne dust can cause defects in precision components. In healthcare, control of bacterial and viral particles is critical for infection prevention.
Even general commercial buildings benefit from monitoring and managing particle loads. Cleaner air means reduced HVAC energy consumption, fewer maintenance issues, and improved occupant wellbeing.
By analysing the types and sizes of airborne particles in a facility, AES Environmental can recommend the most effective filtration solution, balancing efficiency, resistance, and lifespan.
Clean Air by Design
For over 50 years, AES Environmental has combined Australian manufacturing with world-class testing and research. Our filtration systems are designed not only to meet but exceed local and international air quality standards.
From pre-filters that capture coarse dust to HEPA and ULPA systems for critical applications, AES filters are engineered for maximum efficiency, minimal resistance, and proven reliability. All performance data is validated through NATA-accredited testing in accordance with AS 1324 and AS 4260.
Understanding particle size and concentration is central to what we do; it transforms air quality from an invisible concept into measurable, manageable data.
Breathe with Confidence
Every breath carries invisible particles that shape the quality of our air, our health, and our industries. With the right filtration systems, those particles can be controlled, captured, and contained, protecting both people and performance.
At AES Environmental, we translate decades of expertise into solutions that help Australian businesses breathe easier and operate cleaner.
Click here to learn more about our testing and filtration services.