Category Archives: Knowledge Base - Page 2

Webinar Attended – 28 July 2011 Smoke Particulate

The webinar was excellent.  Over 400 people listening to a lecture by a professor and following a power point presentation.  All from the comfort of your own home.

Like any seminar or lecture you have to concentrate and stay awake, but the availability of snacks from your own fridge always helps 🙂

Information about the webinar is available here, and additional information on the topic of smoke particulate matter is shown here.

Certainly a great way to be educated on topics that are not lectured on regularly.

Suspended Particulate Matter Definition – SPM and RSPM

There is much confusion about how to define PM10 particulate, but if articles indicate the definitions they used then the information can be compared with information from other studies. A concern is that the dust measurement equipment for PM10 particulate matter might not be designed to meet the same defined standard as used in the articles which could lead to some discrepancies.

Definitions of PM10 and respirable dust vary from

  • Particulate Matter with diameters less than 10 micron.  Not one particle collected may be above 10 micron, regardless of shape and density.
  • Particulate Matter with an aerodynamic diameter less than 10 micron.  This takes density and shape into account.
  • Particulate Matter with a d50 aerodynamic diameter of less than 10 micron.  This takes density, shape and statistical averaging into account.
  • Particulate Matter with a d50 aerodynamic diameter of less than 7 micron (Mining in South Africa).  This is just a lower cut off used in the South African Mining Sector of South Africa when determining respirable dust levels on workers working on the mines.

Similar confusion exists for the PM2.5 particulate definitions and the equipment used to determine these low particle sizes need to be well maintained and operated by experienced people to prevent contamination of the samples by particulate larger than the defined size.

The fact that respirable suspended particulate matter is more dangerous to health than larger particulate up to 100 micron is well established. It is important to remember though that the ratio of RSPM to SPM will be specific to an area and the measurement of the one should be able to infer the other if the ratio has been experimentally determined, (excluding air pollution modelling).

“RSPMs are more dangerous to health because they are much smaller than Suspended Particulate Matter (SPM), an umbrella term for all such substances with deleterious consequences, that are less than 100 micrometers in diameter.” See this link for the full article

At some stage the definition should be standardised so that apples can be compared to apples.

DustWatch particulate matter equipment measures SPM (suspended particulate matter), and is designed to have a cut-off at 100 micron, so that the maximum particle size collected is as close to 100 micron as possible.  The d50 of the samples is between 35 and 45 micron depending on the sampling location.  This is not an aerodynamic diameter as the size is determined using a Malvern particle size analysis.  So the d50 is the size of particle without taking density and shape into account.

Chris Loans

Mine Ventilation Africa 2011

Mine Ventilation Africa Summit, taking place on 15th & 16th November 2011 in Johannesburg, South Africa.

Also find the links to the website of Mine Ventilation Conferences hosted by IQPC globally –

The effect of heavy & sustained rains on fallout dust monitoring.

The effect of heavy & sustained rains on fallout dust monitoring.


During weather of this type we note:
– General dust levels of agricultural, topsoils or other environmental dusts are lower due to the sources being saturated rather than the water droplets milking out the airborne dust.
– Production dust, however, is not greatly affected as any crushing, blasting or milling operation will still generate dust.
– Because of the above 2 factors the content of fallout dust will now have higher production dust as a percentage content but less in terms of the total dust concentration (the agricultural soil dust is almost non-existent).
– Organic debris will be lower as well.
– Pulverised roadway generated dusts will be lower or almost absent except where heavy traffic dried the surface.
– The sustained rainy & wet conditions have been extensively studied in the Western Cape area which has such rains during winter periods.
– Results can be in the order of 5-10% of the normal dry weather dust conditions.
– The recovery of dust levels will take some time as roads & dusty areas will need to dry out before the dust levels start to increase again.
– During the “recovery” period the first thing that increased is the organic debris & insect debris.
– During extended heavy rain periods the addition of algaecides needs to be increased as the acidic rain addition will encourage the development of algae & other bacterial colony growth. Fortunately these do not add a lot of mass to each sample, but as a percentage this organic material increases a lot as the overall mass remains low.
– Due to the increased humidity of the air production dust will not travel as far as the air density is lower & cannot thus support dust with the result that the precipitation rate gradient is steeper ie. Production dust from a crusher installation will perhaps all precipitate out within 80-100metres (no wind) while in dry weather the material fines could still be in suspension at half a kilometre.
– The d0.50 average particle size of production dust at a given DustWatch position will be finer.
– Remember acid + base = salt & therefore the salinity of the water will increased. This fortunately does not add mass to the sample.

What Is Dust And How Is It Defined?

As dust is fine solids or, in some cases liquids, there needs to be a system of measuring the particulate size and then to categorise the various dusts by size to see to what extent the dust is ingested.

The particulate can be measured by various means but within the metric system of measurements, we use the term micrometer or micron, which is an exceedingly small measurement of one-one thousandth of the millimetre.  The human eye will only see a profusion of dust in the air under certain conditions – predominantly if one is viewing the plume of dust against a blue sky against the light.  This presumes of course, that the dust concerned has a low reflective index and the colour has the greatest contrast with the sky colour as possible.

A lime dust plume is far more visible than cement, which is grey – less of a contrast against the sky’s blue.  Similarly, coal dust will be visible against the sky, whereas a light grey roadway dust will be less visible.

Full Article Here

Dust Is Not Dust. Or Is It?

The information here on dust covers basic information and knowledge that all Environmental Practitioners, Occupational Hygienists, Ventilation Engineers and health professionals, as well as health safety professionals should not only have a working knowledge of, but should be able to apply.  While omitted from the above list, the Architect or Architectural Technologist should equally be aware of and apply the above principles, as the confining of an atmosphere containing dusts will increase the health risk associated with persons moving, living or working in the area or “space” – residential, office or hospital.

Dust by definition can constitute any particulate or matter fine enough to become airborne and will include rock, solid materials, organic substances, vapours, fumes, mists, fogs, smokes and under the correct conditions, fine gravels, flaky material, fibres, moulds, bacteria, microbes or small and sub-micronic insects.

Full Article Here