There is always a lot of jargon and acronyms used to discuss dust and particulates. With the help of our partners Trolex*, who are experts in the manufacture of precise and simultaneous particle monitoring solutions, we look at explaining what some of these terms mean.



Particle Matter

µm - The unit of measurement generally used to describe the size of an individual particle. 1μm or micrometre/micron = 1 millionth of a metre. A human hair is typically around 60μm diameter.

PM - Particulates, or more specifically Particulate Matter (PM) - a mix of solid particles and liquid droplets suspended in air. PM10 refers to all particles of 10μm and below in a sample.

PM2.5 particles are sometimes referred to as ‘fine particles’, and PM2.5–10 as ‘coarse particles’. Fine particles can penetrate deep into the lungs.

NM - Short for nanometre. These are particulate sizes smaller than 1μm. So, the Air XD’s ability to detect a range of particulate sizes from 380nm means it can detect particles sized around a third of 1μm.

g/ml- This measurement refers to particle density or the amount of particulate matter present in a given amount of cubic air. It’s the measurement most frequently referred to in legislation for respirable content. Typically, respirable dust should not exceed 4mg/m3 - equivalent to 4 teaspoons of flour spread over an entire soccer field up to a height of 1m!

ug/m³ & mg/m³ - A measurement of density of particles expressed in mass/volume.

The greater the density of the particle the higher the grams per millilitre.


Particulate Detection Technologies

TEOM: Tapered Element Oscillating Microbalance

A continuous particulate monitoring system, using weight and oscillation to determine the amount of particulate matter present. The more dust present, the slower the oscillation.

TEOM technology is limited in accuracy and requires high levels of regular maintenance to remain functional.

OPC: Optical Particle Counters

A light source projected onto particulates creating a light scatter effect which is measured by a receiver.

Tends to have low accuracy and limited detection range of particulates sizes.

More advanced modern OPC-based instruments such as the Air XD deploy a higher intensity beam and multiple detectors determine full spectrum, real-time presence of particulates as high accuracy levels.

Nephelometer: Very similar to an OPC, but based on the absorption and scattering of light. As the intensity of the transmitted light decreases the more particulates are present.

This technology has very low accuracy and measurement range and requires high levels of regular maintenance.

Photometer: Based on monitoring the changes in light wavelength before and after interacting with particulates. Changes in wavelength indicate the presence of particulate concentrations. The light output is converted into an electrical signal to give a reading.

This technology has very low accuracy and measurement range and requires high levels of regular maintenance.


Frequently Used Terms


Specific to our particulate monitoring range, the chamber through which particulates pass is completely free of obstacles that might lead to the build-up of dust that can compromise the accuracy of the unit.


The area through which the laser-beam interacts with particulates. The wider a scatter-zone, the more information is collected by the light-scatter about particulate size, density and volume.


We use “full-spectrum” to refer to the range of inhalable particulates from 0.35μm to 40μm that can be simultaneously measured by the Air XD.

Dust Suppression

The prevention or reduction of dust dispersion into the air, for example by water or foam sprays. This is not the act of taking dust out of the environment, but making it manageable and no-longer airborne, with a view to making it no longer respirable.

Dust Extraction

The removal of airborne dust particulates, for example through fan extraction.

‘Respirable’ Particulates

Particulates that can be inhaled. These are some of the most dangerous types of particulate, including crystalline silica, for example. Typically, particulates 4.25μm> are respirable.


Diseases and Their Causes

Crystaline Silica

A basic component of soil, sand, and granite, silicate minerals make up over 90% of the earth’s crust. When processed these minerals can produce crystalline silica, a shardy, irregular particulate which can cause diseases including silicosis, lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease.

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A scarring disease of the lungs caused by inhaling fine particles of crystalline silica dust. Silica dust particles can trigger an inflammatory reaction that leads to the formation of lung nodules and scars. These changes can lead to a permanent loss of lung function.

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A chronic lung disease caused by inhaling asbestos fibres. Prolonged exposure to these fibres can cause permanent lung tissue scarring and shortness of breath. Asbestosis symptoms usually don’t appear until many years after continued exposure.

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‘Chronic Obstructive Pulmonary Disease’. The name for a group of lung conditions that cause breathing difficulties. It includes Black Lung Disease, Emphysema (damage to the air sacs in the lungs) and Chronic Bronchitis (long-term inflammation of the airways).

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We hope this has helped provide you with some useful information and guidance about the most frequently used terms in particulate monitoring. Please just get in touch if you have any other questions.


*Information provided by our partner and manufacturer of the AIR XD real-time dust monitor, Trolex.