Particulate matter (commonly referred to as dust or PM) is any size of particle or aerosol that is in the air and can be made up by a wide range of chemical compounds and materials.
These particles can vary greatly in size with the finer PM sizes being categorized into PM2.5 - particles of 2.5micrometres (µm) or smaller and PM10 - particles of 10micrometres (µm) or smaller.
Total Particulate Matter (TPM) is a term used to refer to the mass of all suspended particles which can be captured on a planar filter under particular specified conditions.
Particulate Matter can be from primary sources such as particles being produced from combustion or mineral particles from abrasion; or from secondary sources such as formation in the atmosphere due to chemical reactions that form and condense into particles..
A large amount is produced by transportation, as a mixture from engine combustion, brake/tyre wear and the re-disturbance of road surfaces. Significant quantities are also produced from industrial processes including fuel combustion, construction, and production of materials.
Once in the atmosphere particulate matter can be transported over very long distances where it has the potential to spread into natural environments and contaminate soil and water bodies.
Particulate matter can often be considered toxic, there are extensive links between fine particles (PM2.5 & PM10) alone and as part of other air pollutants, to health problems ranging from aggravated coughing and Asthma symptoms, to more serious respiratory and lung diseases.
Particulate matter is commonly controlled at point sources by the use of filtration abatement systems. For combustion exhaust gases, particulate matter is often entrapped using ceramic or bag filters in chambers. The particles subsequently removed by mechanically shaking or blasting short bursts of air through the filter in a reverse direction (reverse jet), both of which force the dust to drop into a hopper for disposal.
Electrostatic precipitators are also an effective abatement measure in some situations. They are able to entrap dust through applying a highly electrostatic charge to the polluted gas which passes through a series of opposingly charged plates that act to attract the dust and remove them from the gas stream.
Alkali Environmental perform periodic measurements of Total Particulate Matter in ducted emissions from point sources to the standard reference method BS EN 13284-1. The reported results carry UKAS and MCERTS accreditation where the method can be performed to the standard.
These measurements are taken using a manual sampling train whereby a single result is obtained for a gas sample taken from the duct. In combustion gases the reported results are often corrected for oxygen concentration to avoid the affect of dilution air on the result.