Cement Manufacturing Process

Following on from the previous article from ThermoFishcer on the Top 10 Mining articles of 2020, here is the full article on The Cement Manufacturing Process.

Happy reading!

Cement Manufacturing Process


Link to the original article – https://www.thermofisher.com/blog/mining/the-cement-manufacturing-process/?icid=CAD_blog_mining_2020Dec

The Cement Manufacturing Process
By Darrell Leetham

“Different minerals need to be mined in order to make cement. Limestone (containing the mineral calcite), clay, and gypsum make up most of it. The US Geological Survey notes that cement raw materials, especially limestone, are geologically widespread and (luckily) abundant. Domestic cement production has been increasing steadily, from 66.4 million tons in 2010 to about 80.5 million tons of Portland cement in 2014 according to the U.S. Geological Survey 2015 Cement Mineral Commodity Summary. The overall value of sales of cement was about $8.9 billion, most of which was used to make an estimated $48 billion worth of concrete. Most construction projects involve some form of concrete.

There are more than twenty types of cement used to make various specialty concrete, however the most common is Portland cement.

Cement manufacturing is a complex process that begins with mining and then grinding raw materials that include limestone and clay, to a fine powder, called raw meal, which is then heated to a sintering temperature as high as 1450 °C in a cement kiln. In this process, the chemical bonds of the raw materials are broken down and then they are recombined into new compounds. The result is called clinker, which are rounded nodules between 1mm and 25mm across. The clinker is ground to a fine powder in a cement mill and mixed with gypsum to create cement. The powdered cement is then mixed with water and aggregates to form concrete that is used in construction.

Clinker quality depends on raw material composition, which has to be closely monitored to ensure the quality of the cement. Excess free lime, for example, results in undesirable effects such as volume expansion, increased setting time or reduced strength. Several laboratory and online systems can be employed to ensure process control in each step of the cement manufacturing process, including clinker formation.

Several laboratory and online systems can be employed to ensure process control

Laboratory X-Ray Fluorescence (XRF) systems are used by cement QC laboratories to determine major and minor oxides in clinker, cement and raw materials such as limestone, sand and bauxite. Read Analysis of Clinker and Cement with Thermo Scientific ARL OPTIM’X WDXRF Sequential Spectrometer to learn why XRF is the technique of choice for elemental analysis in cement industry. Combination X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) systems accomplish both chemical phase analysis for a more complete characterization of the sample. Clinker phase analysis ensures consistent clinker quality. Such instrumentation can be fitted with several XRF monochromators for major oxides analysis and a compact diffraction (XRD) system which has the capability of measuring quartz in raw meal, free lime (CaO) and clinker phases as well as calcite (CaCO3) in cement.

Read XRF/XRD Combined Instrumentation Can Provide Complete Quality Control of Clinker and Cement to learn more about technology that combines the advantages of both XRF and XRD together.

Cross Belt Analyzers based on Prompt Gamma Neutron Activation Analysis (PGNAA) technology are installed directly on the conveyor belt to measure the entire material stream continuously and in real time to troubleshoot issues in pre-blending stockpile control and quarry management, raw mix proportioning control, and material sorting. Read PGNAA Improves Process and Quality Control in Cement Production to learn what makes PGNAA particularly suited for cement analysis.

Accurate cement production also depends on belt scale systems to monitor output and inventory or regulate product loadout, as well as tramp metal detectors to protect equipment and keep the operation running smoothly. The Cement Manufacturing Process flow chart sums up where in the process each type of technology is making a difference.”




Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Top Mining Articles

ThermoFisher has published an article listing the 10 most read articles on their blog last year.  Interesting read!

Each week we will be publishing one of the top ten in full so make sure you come back next week!


Link to the original article – https://www.thermofisher.com/blog/mining/top-10-mining-articles-this-year/

ThermoFisher Scientific

Top 10 Mining Articles This Year
By Marlene Gasdia-Cochrane, Editor

“Here are the ten most read articles on this mining blog during the past year. Over a quarter of a million people viewed our mining blog this year. Surprisingly, the most read article, with over 47,000 views is a cement-related story. Take a look below and read the ones you missed. Some of them are a bit dated, but are still useful and tens of thousands found them still of great interest.

1. The Cement Manufacturing Process

Cement manufacturing is a complex process that begins with mining and then grinding raw materials that include limestone and clay, to a fine powder, called raw meal, which is then heated to a sintering temperature as high as 1450 °C in a cement kiln. In this process, the chemical bonds of the raw materials are broken down and then they are recombined into new compounds. The result is called clinker, which are rounded nodules between 1mm and 25mm across. The clinker is ground to a fine powder in a cement mill and mixed with gypsum to create cement. The powdered cement is then mixed with water and aggregates to form concrete that is used in construction. Learn about the various laboratory and online systems that can be employed to ensure process control and a quality product.

2. Pyrite: The Real Story Behind “Fool’s Gold”

Pyrite is called “Fool’s Gold” because it resembles gold to the untrained eye. While pyrite has a brass-yellow color and metallic luster similar to gold, pyrite is brittle and will break rather than bend as gold does. Gold leaves a yellow streak, while pyrite’s streak is brownish black. Learn about other reasons this Sulfide mineral is often mistaken for gold, and how XRF analyzers can help identify the real thing.

3. New to the Mining Industry? Make Sure You Know the Most Common Types of Mining Equipment

The most common types of mining equipment vary depending whether the work is being carried out above or below ground or mining for gold, metals, coal or crude oil. From drilling machines to excavators, crushing and grinding equipment – the mining industry comes complete with all the right tools. New to the job and want to find out what it all means? Here’s a few of the industry’s most common types of equipment and why they’re important for the job.

4. Where Will All the Lithium Needed for Electric Cars Be Mined?

There’s a growing demand for lithium-ion (Li-ion) batteries to supply the electric car market. But lithium is a poorly concentrated mineral, so traditional hard-rock mining of lithium-bearing pegmatite and spodumene is a costly and time-intensive endeavor. The easiest and least expensive method of obtaining lithium is by the evaporation of highly concentrated lithium brine. Learn where it’s being found and mined.

5. Where Did Those Gemstones Come From?

Mining for precious colored gemstones is rigorous and time-consuming because the deposits are few and when found, tend to be characterized by small quantities of gems scattered throughout a large amount of rock. Modern mining techniques are of little value in these circumstances, and the deposits are often too small to be profitable for major mine outfits, who leave them to small, independent miners who rely on the same manual techniques they have been using for decades. Nevertheless, in recent years, several major mining companies have entered the gemstone market with new strategies for employing modern mining practice.

6. What Is Ambient Air?

Air quality is an important issue, especially in highly regulated industries such as coal mining, cement processing, and coal‐ and oil‐fired power generation. Rules such the Mercury and Air Toxics Standards (MATS) and the Maximum Achievable Control Technology (MACT) Standards are designed to protect the public and keep ambient air pollution-free. Ozone is another pollutant of ambient air that has been linked to global warming and health risks for children. The 2015 National Ambient Air Quality Standards (NAAQS) for Ozone addresses primary and secondary ozone standard levels.

7. What You Need to Know About Mining Philippines

Mining Philippines, an international conference and exhibition organized by the Philippines Chamber of Mines, showcased the latest products that are advancing the interest of mining, quarrying and mineral processing. According to the show website, attendees learned about the latest technology that can help in “efficient exploration, development and utilization of minerals in consonance with sound economic, environmental and social policies etc. in the Minerals, Metals & Ores industry.

8. Mining and the Environment: What Happens When A Mine Closes?

Mining operations, however expansive and complex, are temporary. Eventually, once the most accessible and valuable materials have been extracted, the mine is closed, and the site must be restored back to its original state. This includes covering up mine entrances, replanting grass and trees, and testing surrounding water, soil, and air for contaminants.

9. Ubiquitous Industrial Minerals: Nature’s Most Popular Raw Materials

Industrial minerals are generally defined as minerals that are not sources of metals, fuel, or gemstones. The most widely-used industrial minerals include limestone, clays, sand, gravel, diatomite, kaolin, bentonite, silica, barite, gypsum, potash, pumice, and talc. Some of the industrial minerals commonly used in construction, such as crushed stone, sand, gravel, and cement, are called aggregates. Industrial minerals are extremely versatile; most have at least two, sometimes many more, applications and span multiple markets.

10. Potash: A Look at the World’s Most Popular Fertilizer

Today, potash comes from either underground or solution mining. Underground potash deposits come from evaporated sea beds. Boring machines dig out the ore, which is transported to the surface to the processing mill, where the raw ore is crushed and refined to extract the potassium salts. When deposits are located very deep in the earth, solution mining is used as an alternative to traditional underground mining. Solution mining employs the use of water or brine to dissolve water soluble minerals such as potash, magnesium or other salts. Wells are drilled down to the salt deposits, and the solvent is injected into the ore body to dissolve it. The solution is then pumped to surface and the minerals are recovered through recrystallization.”


Top Mining Articles

Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Should We Give Dust a Chance?

Should We Give Dust a Chance? The European Nework on Silica says “no”.  Read the following article from nepsi and see what they have to say.


Link to the original article – https://www.nepsi.eu/dont-give-dust-chance

Don’t Give Dust a Chance

nepsi – The European Network on Silica

“Dust is a disperse distribution of solid substances in gases, particularly air, resulting from mechanical processes or from the swirling up of deposits.

With this rather complicated definition a very specific type of hazardous substance is paraphrased which is accorded a particular significance in many branches of industry. In mining, quarries and tunnelling, in the use of dust or powder-like raw materials in the glass and ceramics industry, in metal foundries, in the manufacture and processing of building materials, in the mechanical machining of different raw and finished products, for example as a result of grinding, but also in maintenance and cleaning work in areas with a high accumulation of dust: in all these processes, fine and finest solid particles occur which are released into the air at the workplace and can therefore be inhaled by the people employed there.

The health hazard caused by the inhalation of dust is however usually dramatically underestimated by employees and the responsible management staff in the plant. On the one hand dust is often only considered to be “annoying dirt”, which from time to time needs to be swept away or disposed of – as long as one can still see one’s hands in front of one’s eyes, everything is ok.

On the other hand the matter of dust is old hat, the proverbial “hellholes” belong to the past at any rate, or maybe not?

To be able to effectively confront such catastrophic prejudices and thereby facilitate an effective dust control, a deeper knowledge of the type and mode of action of the different types of dust is necessary.

What dusts are there actually?
As already defined, dust consists of fine, solid particles distributed in the air that are caused by mechanical machining (milling or surface machining) or by the swirling up of deposits (e.g. by blowing off dust with pressurised air or dry sweeping using a broom). Fumes count among dusts in the broad sense. They are formed as a result of chemical or thermal processes (e.g. welding) and also consist of fine solid particles distributed in the air.

Fibre dust is a description of airborne particles made from inorganic or organic substances which have an elongated shape. Fibres which have a length of > 5 µm, a diameter of < 3 µm and exceed a length-diameter ratio of 3:1 play a particular role since only they can penetrate into the deeper respiratory passages.

Dust entering the air at the workplace is inhaled when breathing and thereby reaches the different areas of the respiratory organs. Larger particles are already segregated in the upper air passages, i.e. in the nose and throat, while only the smaller particles reach the deeper respiratory passages, the alveolus or pulmonary alveoli. To assess the health hazard, therefore, in addition to the concentration of particles (dust mass per m³ breathable air in [mg/m³]) the particle size in particular is also of significance.

Two size categories are thereby differentiated: the inhalable and the respirable fraction. Inhalable dust refers to the entire inhalable proportion of the dust through the mouth and nose. Repirable dust relates to the proportion of the respirable dust which can reach the pulmonary alveoli due to its small particle size (fig. 1 and 2).

The individual hazardous substances can, in each case depending on how they originate, occur in entirely different particle fractions and be individually limited in these fractions via the occupational exposure limit (OEL) according to their toxic properties. The assessment of dust that is hazardous to health at the workplace therefore, in addition to the proportions of inhalable and respirable dust, also calls for the knowledge on the distribution of the hazardous substance within the individual fractions. A differentiation must be made according to particle size, shape and material composition (fig.3).

Occupational exposure limits for different varieties of dust have so far been determined according to this principle for the inhalable or for the respirable dust fraction. Irrespective of this there are general upper limits for the inhalable and respirable fraction of dust without specific toxic effect. In the EU no binding OEL has so far been determined for inhalable and respirable dust. However, for inhalable dust a OEL of 10 mg/m³ applies in the majority of EU member states whereas the national values for respirable dust are in a range from 3 to 6 mg/m³. An overview of the internationally applicable OEL´s for dust can be found in www.dguv.de/ifa/de/gestis/limit_values/index.jsp (fig. 4).

How do dusts enter the body and what effect do they have?
Humans have a respiratory system with an effective self-clearance mechanism. This filter system copes with “normal grime” effortlessly and protects humans quite perfectly. However, it is not adequately designed for excessive stress as a result of dusts. An essential function in the self-clearance of the respiratory passages is played by the microscopically-small cilia which can be found inside the bronchia and their finer branches, the bronchioles. With continuous directed movements they transport the dust particles deposited in the bronchial mucus back to the upper respiratory tract where they can then be coughed up.

As a result of inhaling large quantities of dust or of toxic dust, this clearance mechanism can be disrupted or at least be greatly impaired for a long time. The consequences are irritations or inflammations of the upper respiratory passages, increased mucous secretions and a tickly cough, bronchitis and inflammations of the bronchia and of the pulmonary tissue. In these cases, it is much easier for toxic, carcinogenic and allergenic dust particles such as, for example silica dust, heavy metal oxides, welding fumes, wood or flour dust, to deploy their harmful effect in the respiratory passages and in other organs of the body.

Tobacco fumes particularly impair the clearance mechanism of the lungs. Smoking can lead to the destruction of the bronchial mucosa with the irreversible loss of cilia and adenocytes of the respiratory passages that form mucous. The transport of the mucous with the dust particles segregated in it out of the respiratory passages comes to a standstill. Smoking therefore is harmful not only as a result of the toxic substances in the tobacco smoke such as tar constituents, carbon monoxide, formaldehyde, benzene, heavy metals and nicotine. It also disables the self-clearance mechanism of the lungs and thereby multiplies the harmful effect of the inhaled dust.

What regulations are there on dust protection?
The fundamental approach for dust protection is determined in the Chemical Agents Directive 98/24/EC dated 7 April 1998. Accordingly it should be tested whether substances with a lower risk to health can be used (principle of substitution). However, silica as a raw material cannot be replaced in many branches of industry since silicon dioxide is the basic component for an entire series of mineral raw materials and products. Other frequently used hazardous dusts (e.g. lead oxide in glazes and engobes) can sometimes be replaced by other less harmful compounds.

If hazardous substances cannot be substituted, protective measures are to be taken. The order of precedence of the protective measures is also defined in the Chemical Agents Directive. Work methods are to be designed in such a way that hazardous vapours and suspended particles are not released. Leaking of generated dust can be prevented, for example, by means of dust-tight systems or vacuum operation. The design of the working process is therefore to be reviewed. For example, the use of moistened raw materials can drastically reduce the production of dust. Another possibility is the use of raw material granulates with a corresponding lower tendency to dust formation.

According to the current state of the art the release of dust is unavoidable in many production areas. For this reason capture must be as complete as possible already at the emission point or point of origin. There are already suitable extraction systems, for example, for ceramic presses, for bagging units for powdery substances or tools and systems for the machining of natural stone. The effectiveness of extraction systems must be supported with corresponding ventilation technology and adequate venting of the work areas. Substances which tend to produce dust must be immediately disposed of by suitable means (vacuum cleaners or sweeping vacuum machines with deduster) in the event of repair works. Brooms or even pressurised air are not suitable and are to be strictly banned from such areas!

If the OEL´s, despite exploiting all technical and organisational protective measures, are not complied with, for example during maintenance and repair work, then personal protective measures are necessary, for example wearing dust masks.

In any event employees must be trained in accordance with the Chemical Agents Directive about hazards and protective measures: the preparation of operating instructions and corresponding instruction by supervisors are compulsory. Further organisational measures in the event of dust exposure include the execution of specific occupational health check-ups or the minimisation of exposure by restricting the duration of stay of the employees (e.g. in a partially or fully-automated raw material dosing system).

What is the situation in practice?
The relatively extensive and thus general provisions of the Chemical Agents Directive 98/24/EC are further substantiated in the EU member states in national legislation. These regulations, however, often are not sufficient to solve urgent dust problems in operational practice. For this reason the Expert Committee for glass and ceramics have prepared “Ten golden rules for dust control”, which should provide plants with a simple, clear and above all user-friendly guideline. These rules can be used by the responsible parties in the plant for the risk assessment, for training purposes and in daily work.

If the rules are observed by the employees, they will achieve a major contribution to the reduction of dust exposure and thus improve the protection of health in the plants.

10 Golden Rules – follow the link provided – https://www.nepsi.eu/dont-give-dust-chance#accordeon – to read these in full

1. Avoid the formation of dust in the first place
2.Use low-dust Materials
3. Work in closed systems wherever possible
4. Immediately separate dust at the point of origin
5. Optimise and regularly maintain extraction systems
6. Adequately ventilate the workshops
7. Immediately dispose of waste in a dust-free manner
8. Regularly clean workplaces
9. Keep work clothes clean
10. Use respiratory protection for dust-intensive work”


Should We Give Dust a Chance?

Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

The Truth About Dust

Last time we read that dust wasn’t so bad, now let’s read this article from the Karolinsak Institute and learn “The dirty truth about dust”


Follow this link for the original article – https://ki.se/en/research/the-dirty-truth-about-dust

Karolinska Institute – Research

The dirty truth about dust
“Some people say that no one has ever died from a little dust. On the contrary, say others, dust is deadly. In reality, not all dust can be tarred with the same brush. Here is your guide to the dirt on earth – and on the moon.

When Neil Armstrong and the other astronauts walked on the moon in the 1960s and 70s, small clouds of moon dust puffed up around each footstep. It really flew up when they went for a drive in the moon buggy. So much so that they were forced to stop and build an improvised mudflap with material from the moon lander.

Back in the space capsule, they took off their dirty spacesuits as if was any other day at work. In pictures from inside the space capsule, the astronaut Eugene Cernan looks like a happy miner, covered in dust and with a big smile on his face.

But extraterrestrial dust is not like other dust. The astronauts noted that it smelled remarkably strongly of burned gunpowder. And it stuck to everything. The astronaut Jack Schmitt was the first to be affected by a mysterious space cold.

“It was really crazy how they acted, that they didn’t store the spacesuits separately. We now consider moon dust to be very hazardous,” explains Lars Karlsson, researcher at the Department of Physiology and Pharmacology, Karolinska Institutet.

The dust has been described as being fine as flour, but as rough as sandpaper. It is thought to have been created through millions of years of bombardment by micrometeorites that have partly transformed the top layer of stone into glass. Further meteorites have then crushed this glass into increasingly fine particles.

Lars Karlsson, who is conducting research concerning human physiology in space, describes how moon dust is a serious impediment to future moon landings. Together with an international research team, he has analysed how moon dust is thought to affect the human body. According to the researchers’ hypotheses, moon dust has pretty much all of the bad properties dust can have.

“Firstly, it consists of very sharp particles that cut into the tissues. Secondly, it is irradiated with cosmic radiation, which we believe makes it electrically charged and hyper-reactive – this means that it sticks to everything and reacts chemically with everything it comes into contact with. Thirdly, it contains many small particles that can penetrate barriers such as human skin and lung tissue,” says Lars Karlsson.

Combined with low or non-existent gravity, which means that the dust that is stirred up does not fall down again, this makes it really problematic.

Is there anything like moon dust on earth?

“No, not even the moon dust that has been brought back to earth is like moon dust any more. When it reacts with the earth’s atmosphere, its properties change. Attempts have been made to preserve it in airtight containers, but without success. The closest thing to moon dust that exists on earth is newly formed ash from volcanoes,” says Lars Karlsson.

His is one of few researchers who have the opportunity to gain access to moon dust. Together with his colleague Dag Linnarsson, he is now attempting to get the funding together to return it to its original state and study it further. The fact is there is interest from NASA and other space financiers to learn more about the properties and health effects of moon dust. Because one thing is clear – if humans are to return to the moon, the dust issue must be resolved.

On the earth the windy atmosphere and the rain mean that dust particles become rounded and precipitation and gravity mean that the dust eventually ends up on the ground. The dust is not electrically charged and the oxygen in the air means that it is not as chemically aggressive as it is on the moon. But even here, some groups of workers are exposed to chemically reactive dust, for example siliceous dust in the stone industry.

And visiting something that looks similar to a lunar landscape does not require space travel. All you have to do is take a walk to Torsplan in Stockholm, where you will find one of Europe’s largest construction sites. The construction of the new Karolinska University Hospital and its new neighbouring blocks looks, in places, like a bomb site. Which it is actually – the air smells strongly of burned gunpowder after the most recent explosion.

Towering above the disarray is a newly constructed building on the tenth floor of which industrial hygienist Pernilla Wiebert has her office. She works at the Centre of Occupational and Environmental Medicine at Stockholm County Council, helping patients who suffer from work-related health problems, and she conducts research concerning dust and occupational health problems at the Institute of Environmental Medicine, Karolinska Institutet.

The premises are quiet, bright and fresh. The patients, some of whom have developed a sensitivity to dust and strong smells, are received on wooden chairs that are easy to keep clean.

“We have a very good cleaner here,” says Pernilla Wiebert. She explains that some of the patients have been exposed to quartz dust, which is still a significant work environment problem in the construction industry.

As with moon dust, quartz dust consists of hard particles of silica that the body cannot break down. The particles are instead encapsulated in scar tissue in the pulmonary alveoli, which leads in the long term to solidified lungs and the incurable disease silicosis.

“In the long term, silicosis is a deadly disease, so it is serious,” explains Pernilla Wiebert.

Quartz dust also increases the risk of the lung disease COPD, which is more common among construction workers than others. The fact that it is carcinogenic is also known because of studies such as that at Gustavsberg’s porcelain factory, where the levels of quartz dust were ten times higher than the limit value in the 1970s and 80s. When Pernilla Wiebert and her research colleagues investigated the incidence of cancer among former employees, it was shown that more of them than normal had contracted lung cancer, as well as urinary tract cancers. Quartz is present in the bedrock and soil in Sweden and in products such a concrete, ceramic and glass. The problem of quartz dust is greatest in the construction industry and mining and stone industry, but is also found in industries such as agriculture and cleaning work such as sandblasting.

The other day she visited the construction site on the other side of the street and was “really impressed” by the efforts being made in terms of the working environment. But in general, she is not at all satisfied.

“Exposure to dust has decreased since the problem was first noted, but we are now seeing an increase in the problem again. Those people who were committed to this problem have subsequently been replaced and it is so much easier to focus on the risk of accidents. Dust is more deceptive as it effects people in the long term,” she says.

Protecting yourself requires good cleaning procedures and the use of a breathing mask – and the beard has to go.

“A breathing mask must fit tightly and works poorly when you have a beard or stubble. There are good ways to protect yourself, but such important details are often neglected. If only the knowledge we have had been used, there would not be a problem,” says Pernilla Wiebert.

Dust is also deceptive, as the most common type can neither be seen nor smelled. Larger particles can certainly worsen asthma and cause allergies, if they contain allergens.

But the cilia in the airways are able to quickly transport them to the throat where they are swallowed, and they are clearly noticeable as an irritation in the nose and throat. Small particles, that are found in dust such as quartz dust, reach as far down as the lungs’ capillaries and alveoli, where they remain for a longer period or are encapsulated permanently.

It is uncertain to what extent small particles penetrate even further, past the lungs, and where they end up. In order to answer this question, Pernilla Wiebert, as part of the work on her thesis, is using an apparatus that generates a cloud of carbon particles, every one of which is labelled with a radioactive isotope that makes it traceable. The radioactive carbon cloud is then inhaled by test subjects.

“I thought that some of the particles would perhaps enter the bloodstream. But it was shown that almost all of the particles, even the smallest, remained in the lungs,” she says.

That was the case with the carbon cloud specifically. But other researchers have found inhaled nanoparticles in organs such as the liver, kidneys and brain. Even if the particles normally remain in the lungs, this does not mean that they are otherwise harmless to the body. Inflammation in the lungs can lead to inflammation in the cardiovascular system and myocardial infarction; something that is more common within occupations with a high level of exposure to particles. The risk is particularly high within occupations with a high level of exposure to small particles from combustion, such as engine exhaust.

Pernilla Wiebert is currently working on a research project that compares the incidence of myocardial infarction in various occupations with data concerning exposure to particles – the goal is to gain new knowledge about which types of particles are most hazardous.

Dust with a biological origin may contain, for example, animal proteins, bacteria and fungal spores, and in high doses can cause influenza-like symptoms known as ODTS (organic dust toxic syndrome). Long-term inhalation can cause inflammatory changes in the lungs that researchers call extrinsic allergic alveolitis, but in specific occupations may go by names such as farmer’s lung, bird fancier’s lung and cheese washer’s lung.

The dust that is formed in pigsties is particularly nasty. Swineherd’s have an increased risk of developing ODTS, as well as the lung diseases chronic bronchitis and COPD, which normally affect mainly smokers. Lena Palmberg, researcher at the Institute for Environmental Medicine, has shown that swineherds have an impaired natural immune response and a chronic inflammation in the respiratory tract. Test subjects who try out the work temporarily also quickly get sharply increased levels of white blood cells and the signs of respiratory tract inflammation. The research indicates that it is bacteria or bacterial components from the pigs’ excrement that is having a detrimental impact on the lungs of swineherds.

Even those who do not have dusty occupations are unavoidably exposed to dust in the home and outdoor environments. Common household dust consists largely of relatively harmless fragments of dead skin and textile fibres. But if the dust contains substances that disrupt hormones or other chemicals from the surroundings, there is a fear that this may lead to a serious impact on health in the long term.

This is currently being investigated in several studies at Karolinska Institutet, among them a project in which dust in preschools is being analysed. The confirmed health effects are even greater when it comes to dust outdoors. However, as opposed to dusty occupations, where a few individuals have a markedly increased risk of becoming ill, dusty cities lead to a fairly small increase in various health risks, but for a large number of people.

“For an individual, the increase in risk is not particularly large. But when looking at the entire population, particles in the air cause many premature deaths each year,” says Tom Bellander, professor of environmental epidemiology at the Institute for Environmental Medicine, Karolinska Institutet.

In spring, cities become particularly dusty as the streets dry out and the particles that have been stored by damp roads over winter are stirred up into the air. Small particles from combustion are generally regarded as having the most serious health effects. In recent years, however, the perception that larger particles, such as those that arise when studded tires wear the road, would at worst be an irritant, has been re-evaluated. “We know now, from studies of environments in which sand from the Sahara often blows in, that larger particles also contribute to increased mortality,” says Tom Bellander.

According to Tom Bellander, it is generally very difficult to determine what makes a particular particle harmful and to measure exactly which particles are responsible for the detrimental health effects. The guidelines that are used to regulate particle levels in the air focus on the particles’ size. The World Health Organisation’s guidelines state, for example, that the air should not contain more than 10 micrograms per cubic metre of particles that are up to 2.5 micrometres in size in the long term. There are also statutory standards for these and for somewhat larger particles. But Tom Bellander believes that a major deficiency with the guidelines is that they do not take greater account of the shape, origin and chemical properties of the particles. Quite simply, we do not know enough to enable this.

At the political level, Tom Bellander believes that there is a lot to do if we are to reduce the level of particles in the air. The goal should be to reduce emissions and move them from environments in which people live. As an individual, there is not much you can do aside from living in a place that is as clean as possible.

“If you live in Beijing, Delhi or Mexico City, I think this is something very relevant to be thinking about. In Sweden, this is really more one factor among others to think about when you plan to move, provided you do not have a specific sensitivity that gives you problems.”

But understandably, the advice to move cannot be followed by everyone.

“The emissions are where the people are. So if everyone moved out of the city centre, it won’t be long before a large proportion of the air pollution moves too.”

Info: This is why dust can be harmful
Dust can consist of almost anything and be harmless or deadly. Here are some properties of dust particles that govern their impact on health.

Size – Small particles such as exhaust particles float for longer in the air, are more easily inhaled and get deeper into the lungs.

Shape – Particles with a large surface area such as moon dust have a greater risk of reacting with the body’s cells and tissues.

Reactivity – The surface of particles can be chemically reactive or stable. This determines what reactions can take place when they come into contact with the human body.

Lifespan – Some particles can be broken down by the body, others cannot. For example, quartz dust remains in the body, which increases the risk of some health effects.

Info: This is where dust particles are found
Dust can consist of, for example, pollen, bacteria, smoke, ash, salt crystals from the sea and small pieces of dirt or stone.

There is often a grain of dust in the middle of a raindrop. Raindrops are actually formed around small grains of dust or particles in the atmosphere known as aerosols.

The more dust the air contains, the prettier the sunset. This is because particles help to disperse blue light and let through more of the red colours.

The Sahara Desert is the greatest source of dust in the world. Every year, 180 million tonnes are blown out over the Atlantic. Some reaches South America, where it helps to fertilise the Amazon Rain Forest.

Text: Ola Danielsson, first published in Medicinsk Vetenskap, 2 2016″


Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Dust – Good for you?

Can dust and dirt be good for you?  Have a look.  Enjoy the read!


Link to the original article – https://www.thestar.com/life/health_wellness/news_research/2011/05/16/dust_might_be_good_for_you_study.html

Dust might be good for you: study

By Eric DanekThe Canadian Press
Mon., May 16, 2011

“MONTREAL – Didn’t get around to dusting this weekend? Don’t worry. It turns out that dust might actually hold some benefits for you.

The perennial household nuisance actually purifies the air by neutralizing ozone that can harm our lungs.

Dust can do this because one of its major components is human skin — which contains the ozone-eliminating component squalene.

So don’t feel too bad about the fact that bits of your body are accumulating on the DVD player.

“Dust is parts of . . . people that have been in that room,” said Charles Weschler, who helped author a study, the result of which were announced this week by the American Chemical Society.

“I mean, that’s a gross way of thinking about it.”

Humans constantly shed their skin, losing up to 500 million cells per day. At that rate, according to Weschler, it would take a person two to four weeks to turn over all of the skin cells on their body.

It’s these skin flakes that clean the air. Their squalene helps neutralize ozone.

Most people might think of ozone as a good thing — and it is, when it’s up high in the atmosphere and protecting us from ultraviolet radiation. But when it’s down here, closer to us in the air that we breathe, it’s a pollutant.

According to the Canadian Centre for Occupational Health and Safety, even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs.

In their study, published in the peer-reviewed journal Environmental Science and Technology, Weschler and colleagues studied the potential of ozone removal by dust in Danish homes and daycares.

They found the reduction of ozone could be anywhere from two to 15 per cent, depending on the amount of squalene present in the dust.

The benefits could be even greater.

Weschler’s study only looked at the squalene in settled dust. He thinks that squalene from dust can also stick to surfaces like windows or desks, and this squalene coating could lead to a higher-than-calculated ozone reduction.

Dust isn’t the only source of squalene in our environment. We’re literally covered in it.

“The skin oils on our surface, (the) skin oils on our forehead, or our nose or the oils responsible for us leaving fingerprints behind, those skin oils contain squalene,” said Weschler, a professor at the School of Public Health at the UMDNJ-Robert Wood Johnson Medical School in New Jersey.

“Squalene is actually the single most abundant chemical in our skin surface (oils).”

He calls human beings, “remarkably good ozone sinks.”
But before you pack away that feather-duster forever, there are some caveats.

Of course, lower ozone levels will hardly provide comfort to your guests with dust allergies who wind up hacking and wheezing when they come over.

And not much is known about the health effects of the compounds formed when squalene and ozone react with each other.”


Link to the original article – https://www.marksdailyapple.com/going-grubby-the-primal-benefits-of-dirt-dust-dishevelment/

Mark’s Daily Apple

Going Grubby: The Primal Benefits of Dirt, Dust and Dishevelment

“Clearly, cleanliness is next to godliness, as they say, in this country. The number of products devoted to the sacred rite of purging and scouring American households staggers the imagination. (Ever roamed the cleaning supply aisles at Target? It’s a trip unto itself.) Every strength, size, scent, packaging, active ingredient, and formula (Would you prefer powder, gel, spray, cream, or specially concentrated disk?). But wait! There’s the anti-bacterial, virus-killing, and “odor shielding” options. And, of course, we now have a plethora of “green” cleaners infiltrating the line up. (Some more green than others.)

But just what do we get for the infinite invention of the last thirty or so years? Are our living quarters really all that much cleaner than our grandmother’s homes? Have we truly transcended the power of elbow grease, hot water, and simple routine?

While basic sanitation has clearly made a critical difference in human health, what happens when old-fashioned diligence becomes super strength obsession?

We all remember learning in school that 90% of household dust is made up of sloughed human skin. Yeah, it grossed us out, but is it really such a major health threat that we use language suggestive of military assault to “combat” it? We tend to think that there are some useful things in there. How about pet dander? Numerous studies have shown that exposure to pet dander throughout childhood reduces the incidence of pet allergy and asthma.

We agree that if you can write “wash me” in the dust on your window sill it’s time to dig out the Swifter. (We didn’t say we were fans of filth.) Keeping a handle on the dust that accumulates is important, we think, but not because of the heebie jeebies elicited by the skin statistic or any aesthetic reasoning. It’s those nasty flame retardant particles (PBDEs) that get kicked up from furniture and other household items we talked about a couple of weeks ago. (Suddenly that human skin sounds pretty good.) Nonetheless, we don’t believe in flying off the handle. Cut out conventional flame retardant products where you can and happily retire the white glove test.

O.K., this one’s our favorite. We could write an entire post “Ode to Dirt.” Suffice it to say, since our long lost days of mud pies, too many of us have forgone the unique pleasure of luxuriating in nature’s emollient.

For anyone who’s had a mud mask or massage, you likely need little convincing. For those of you who lived in the mud as children much to the desperate chagrin of your mothers, we know the love isn’t something you truly outgrow. (You wouldn’t happen to be outdoorsmen/women now would you?) But if you don’t fall into these categories, consider that your run-of-the-mill, basic, unassuming, backyard soil can act as an anti-depressant? You bet your buckets! Naturally occurring bacteria in the soil, it turns out, trip the neurons that produce serotonin.

As for soap, consider it overrated. There’s genius in that skin of ours – a nifty little “acid mantle,” to be specific, that protects the skin from dehydration, inflammation, and cracking that leaves it open to infection.

As for the typical household cleaners designed to rid your house of every speck of dirt that may trespass beyond your doorway? Well, as we said in our chemical load post, the endocrine-disrupting and respiratory damaging chemicals that make up so much of those products seem to be a much greater threat (understatement) than the good old dirt that Grok lived, ate and breathed.

O.K. We don’t have much of a “health” argument to make with this one. In fact, household clutter has even been linked to higher obesity rates. However, in light of the “clean” obsession, are we overdoing it on this front too? There’s the part in Ferris Bueller’s Day Off when Ferris describes Cameron’s house (to paraphrase): It’s like a museum. It’s very beautiful, but you don’t dare touch anything.

In Grok’s day (and perhaps in our grandmothers’) it was probably easier to keep a clean house because – well – people just didn’t accumulate as much stuff. In the age of Rubbermaid bins and The Container Store, isn’t it so easy to just keep adding to the collection as long as everything ends up with a place to “live,” as professional organizers call it?

We think there’s a place for dishevelment to be sure. To affirm the old adage, recent research suggests that the owners of messy offices are more creative than those with very neat spaces. Apparently, the proverbial, creative, “light-bulb” moments tend to come as a result of mental happenstance. The mind finds momentary distraction in a “side track” thought (or random unearthed document) and has the chance to make new and novel connections. Sound true to you?

In the spirit of good old Mother Nature, the opposite of dishevelment isn’t meticulous organization. In one setting, one moment, it’s layer upon layer of rich detail. Stark spareness in another. (Perhaps there’s something to living with both possibilities. Hmmm?) In either and any case, it’s messy, dirty, dusty, rough, ragged and will probably leave a mark. In the postmodern, super sanitized, Fabreeze-misted world of Mr. Clean versus Grok, thanks, but we’ll hang with Grok any day of the week.”



Dust - Good for you?

Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Laundry Detergents and Pollution

An interesting article from Sciencing.com about pollution and laundry detergents.  Enjoy the read!

Laundry Detergents and Pollution

By Emily Beach

“In the quest to get whites their whitest and keep colors bright, you could be contributing to air and water pollution that affects both human health and the environment. Yes, your choice of laundry detergent can have a direct impact on the quality and health of your local lakes, streams and water supply. Understanding how different chemicals and other ingredients can affect the Earth can help you make informed, Earth-friendly choices in the laundry detergent aisle.

Laundry detergent has contributed to environmental pollution ever since it was first introduced during the early 20th century. For years, detergent makers used chemicals called phosphates to make their products. When the phosphates used in detergents enter local water supplies, they provide nutrients for marine plants, resulting in algae population explosions. The algae use up the oxygen in the water, leaving none left for fish and other animals to breathe. These bodies of water become barren habitats and unsuitable for human recreation.

By the 1990s, many states banned phosphates in detergents. In 1994, the detergent industry agreed to strictly limit or remove phosphates from their products. Water tests performed in the 1970s showed that the level of phosphates in wastewater jumped to nearly four times the level of the 1940s. After the phosphate bans of the 1990s, levels dropped by more than half.

Pollution Concerns
Though you won’t find phosphates in most U.S. laundry detergents, many of these products contain other substances known to pollute the environment. Nonylphenol ethoxylates and other chemicals used to make detergents are toxic to marine life. According to the U.S. Environmental Protection Agency, they also affect human development and reproduction .

Sodium perborate and other detergent bleach products can irritate the nose, eyes, lungs and skin and might affect reproductive health. Some dyes used in laundry detergents are toxic to fish and other aquatic life; others are known carcinogens, according to the EPA.

Indoor Air Quality
Many of the concerns about laundry detergents relate to how they affect the water supply or marine life after they leave your home. However, laundry detergents can also damage air quality in and around your home.

Science Daily reports a study of dryer vent exhaust gas, which found traces of many organic compounds, including carcinogens such as acetaldehyde and benzene. These compounds, which are used to scent some popular brands of laundry detergent, decrease air quality indoors and contribute to air and water pollution in the environment.

You’ll find many eco-friendly detergents on the market that claim to protect the environment. When you compare detergents to spot potentially harmful ingredients, read labels carefully. To quickly identify more Earth-friendly laundry detergent options, look for products bearing the EPA Design for the Environment seal. Detergents with this seal are free of inorganic phosphates and contain only surfactants that minimize environmental pollution when they go into solution. To protect your family’s health, WebMD recommends seeking out laundry detergents that are fragrance-free or scented without the use of petroleum by-products.”


Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

How to Define PM10 Particulate

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


Information below sourced from – NSW Government – Health

Particulate matter (PM10 and PM2.5)

“Particulate matter, also known as particle pollution or PM, is a term that describes extremely small solid particles and liquid droplets suspended in air. Particulate matter can be made up of a variety of components including nitrates, sulphates, organic chemicals, metals, soil or dust particles, and allergens (such as fragments of pollen or mould spores). Particle pollution mainly comes from motor vehicles, wood burning heaters and industry. During bushfires or dust storms, particle pollution can reach extremely high concentrations

The size of particles affects their potential to cause health problems:

PM10 (particles with a diameter of 10 micrometres or less): these particles are small enough to pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects.

PM2.5 (particles with a diameter of 2.5 micrometres or less): these particles are so small they can get deep into the lungs and into the bloodstream. There is sufficient evidence that exposure to PM2.5 over long periods (years) can cause adverse health effects. Note that PM10 includes PM2.5.

Potential health effects from exposure to particulate matter:
There are many health effects from exposure to particulate matter. Numerous studies have showed associations between exposure to particles and increased hospital admissions as well as death from heart or lung diseases. Despite extensive epidemiological research, there is currently no evidence of a threshold below which exposure to particulate matter does not cause any health effects. Health effects can occur after both short and long-term exposure to particulate matter.”


Particulate Matter - How to Define PM10 Particulate


Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Dust Explosions

We recently published an article on the dangers of dust and that dust can, in fact, cause explosions.  Here is a little video showing an experiment – dust in the form of flour shown to combust.

This information from – Robovent

“Dust explosions occur when combustible dusts build up in the air and combust rapidly, causing a strong pressure wave to form. They are a deadly hazard in a variety of workplaces, from grain silos to plastics factories. A dust explosion requires several factors to be present at once. These include:

A combustible dust at the right concentration level
An enclosed space
An ignition source

Sometimes these factors are combined into a graphic known as the “Dust Explosion Pentagon.” The component in this graphic called “dispersion” is also known as concentration. If a concentration of dust is too low, there is not enough of it present to fuel an explosion. If the concentration is too high, there is not enough oxygen to support combustion.

Dust Fire and Explosion Pentagon - Dust Explosions

While some combustible dusts are easy to guess—wood and paper dust, for example—others aren’t, such as aluminum dust. Combustible dusts become more dangerous as particulates become finer. These dusts feature a high ratio of surface area to volume, adding to their combustibility. When these dusts combine with oxygen within a range of concentrations, a dust explosion is possible.

In these conditions, all that is needed for an explosion is an ignition source. This source can be anything from a cigarette to a spark to an overheated wheel bearing. Under the right conditions, some combustible dusts can self-ignite as a result of static that builds up as particulates rub against one another. The ignition causes the dust to combust quickly—a process called deflagration that creates a wave of high air pressure. Sometimes this explosion can stir dust that has settled in the space, creating a cloud of new dust—a fuel source for an enormous secondary explosion. A dust explosion can blow out walls in a facility and kill or injure workers within the space or nearby.”


Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Why Dust in Monitored

Why Dust is Monitored

Industrial dust can explode.  These occur when a large build up of combustible dust is dispersed into the air and then explode if provided with an ignition source.  Immense damage and loss of life can follow. (See video – https://www.csb.gov/csb-releases-new-safety-video-inferno-dust-explosion-at-imperial-sugar/)

Other dangers that industrial dust pose are lung diseases caused by the inhalation and retention of dust in the lungs. Coal miners especially are exposed to many kinds of dusts including silica. Tiny particles of coal dust are retained in the alveoli – they are surrounded by macrophages but, eventually, the system is overwhelmed and an immune response follows.

It is impossible to prevent all industrial dust diseases but they can be reduced by various safety precautions, such as adequate ventilation, keeping down dust levels and wearing of facemasks.

An extremely important factor in prevention of dust related problems is the monitoring of dust using specially engineered equipment. Dust monitoring equipment assist industry and agriculture in detecting harmful levels of toxic dust which in turn allows the problem to be engineered away.

Dust not only causes health and safety problems but can also cost industry money in terms of equipment maintenance and production. See the extract below from the website http://www.dust-monitoring-equipment.com/services/dustdesign.htm  : “We have successfully removed fish scales from marine diamond deposits with specialized dust control equipment.   The fish scales were not actually a dust problem but they did interfere with the optics used to separate diamonds. This is similar to the problem where we had to de-fluff diamond concentrates from underground mining operations, where a slurry explosive is pre-packed in plastic bags. The slivers of plastic fluoresced in the same way that diamonds fluoresce and needed to be removed from the process.”

In general finer suspended dust remains airborne almost indefinitely due to air currents and thermal activities on any given day, even if there is no wind at all. The unit that we use to capture this dust is the DustWatch, designed and patented in South Africa by Gerry Kuhn Environmental and Hygiene Engineering.

The use of fall-out monitoring yields a large amount of information, allowing a far greater and effective study to be undertaken than any other single sampling method. If used in combination with PM10 or total particulate dust sampling, results can be very conclusive.

Why Dust in Monitored - Dust Bucket - Fallout dust monitoring - DustWatch

Why dust is monitored


Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

Dust Defined

Dust Defined – The following information comes from one of our own articles.  What exactly is dust?  Take a look below – for the full article please follow the link – http://dust-monitoring-equipment.com/training-presentation-dust-is-not-dust.htm

Dust 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.


Any existence of moisture within the emission will also increase the dust visibility:-


* By physically wetting the particle, which then may become darker in colour.
* By condensing and adding a visible dimension to the plume.  Most observers will comment on how bad a dust plume looks when they are in fact seeing steam or water vapour, which they presume is white smoke rather than what it is – water vapour.  As a rule of thumb, watch such a plume and if it suddenly starts to disappear, then you are seeing water vapour.  What remains in the air is dust and this may just be visible at a distance further than the vapour plume extremity.


Dust of differing size particulate has a system of descriptive classification, which, while rather subjective, does put a lot of light on the matter and enables us to obtain a good idea of the particle size range applicable for each category.


The following diagram 1, of which there are many examples with slight variations, is most handy to convey the concept of particulate sizing within each category by definition.




As soon as one starts to view the various dust sizes, further classification by various agencies come into the picture due to the need to monitor for health purposes or for other reasons.


Occupationally, in South Africa we need to be aware that there are categories for:


* Respirable dust
* Thoracic dust
* Inhaleable dust
* Nuisance dust.


While the last description may not be that official it is used by all and sundry as a “one size fits all” approach, as we all hate dust with one or two exceptions – “Gold Dust” or perhaps “Diamond Dust”.  To define any dust one needs to specify the dust particulate size range not withstanding the reasonably hard and fast definitions outlined above.  The American Conference of Governmental Industrial Hygienists (ACGIH), now considered to be one of the foremost authorities on industrial hygiene and contrary to its name, is a private not-for-profit non-governmental corporation, whose members are industrial and occupational hygienists and other safety and health professionals dedicated to the promotion of health, safety and health safety in the workplace, has established the indicated classifications based on the following criteria:-


SIZE DISTRIBUTION Aerodynamic diameter (d) Mass % Aerodynamic diameter (d) Mass % Aerodynamic diameter (d) Mass %


































































DEFINED SIZE d0,50 = 100µm d0,50 = 10µm d0,50 = 4µm




The term or definition of total dust is “airborne material sampled with the 37mm closed face cassette traditionally used for aerosol sampling”.  The term will ultimately need to be replaced occupationally by one of the above descriptions.  Research using cassettes has broadly indicated  it is scandalous that we still ‘assume’ this total dust is a risk or not after over 40 years.  It can be ingested.


We point out that the three categories of particulate size sampling are achieved using the new ISO/CEN/ACGIH curve cyclone with a flow rate of 2,208 litres/min (say 2,2 litres/min).  The previous BMRC curve cyclones were operated at a flow rate of 1,890 litres/min (say 1,9 litres/min).


During the initial stages of the swap-over to ISO/CEN/ACGIH cyclones, we noted that paired rigs yielded a d0,50 cut off of 4,00µm for the BRMC and 5,0µm for the latter.  This was largely due to the differing flow rates and if the ISO/CEN/ACGIH was operated at 1,9 litres/min then a value closer to the BRMC 4,00µm was achieved.  So why increase the flow rate?  Research has now found larger particulate trapped in lung tissue.


The above information is handy for occupational hygienists to determine PM10 levels using ISO/CEN/ACGIH cyclones and 37mm cassettes and monitoring for environmental purposes.


When using the cassette without the cyclone at 1,90 litres/min, one achieves a PM10 result, but to improve the distribution of dust on to the filter, the distance between the cassette entrance hole and filter needs to be increased so a more lamina distribution can be achieved as well as a more consistent loading of the filter.  Any material entering and remaining loosely in the bottom of the cassettes must not be retained in the sample as this will be average oversize and considerably so.


It is possible to take a larger cut-off at perhaps d0,50 – 20µm, 30µm or even 50µm, but if we bear in mind that the limiting factor after 2,0 litres/min becomes the cassette opening, which needs to be drilled out to 6mm for 20µm and 30µm and to 10mm for 50µm dust, then one is sacrificing cassettes.  The flow rates also become increasingly critical the larger particulate we wish to capture and one then needs to consider the density of the dust material to arrive at a flow rate.




Well, to start off, we need to go back and notice how we accepted the particulate sizing and flow rates so easily and assumed that these are finite, cut and dried and cast in stone as it were!!!


No, life is never that simple and air density played a massive role in the amount of air that our gravimetric sampler was handling, and in fact the altitude will also have played a massive role, as well as barometric pressure, so at the end of the day, how accurate are those Respirable, Thoracic or Inhalable dust samples, and while we are at it, how accurate is your high volume constant flow sampler determining PM10 sample results?  It has become question after question with fewer and fewer answers being available, which means that the environmental auditors who check your reports will only specify and check that your methodology was to regulation or method.  Where has reality gone?  Dust is not dust, is not dust, or is it?


While we are on Question Time, let us select a few more to look at:-


* If your PM10 or gravimetric sampling rig sampler is operating to spec and the dust is mainly organic, are you over reading or under reading?  Does Durban and Johannesburg make a difference?
* The same question needs to be asked for gravimetric sampling, but let us add common pollutants to make the answer more difficult.  If your gravimetric sampler and ISO/CEN/ACGIH cyclone and cassette are running at 2,2 litres/min with cellulose wood fibre dust and coal dust, will the results be the same and will both be representative bearing in mind that the density of wood fibre could be as low as 20 kg/m3, while the coal dust will have a density of over 2 ton/m3?  I have used bulk density and not material density.  Is this correct?


Having questioned convention surrounding capturing the airborne dust for your sample, let us look at how the dust is scavenged or collected.


The inlet on an ISO/CEN/ACGIH cyclone is exceedingly small and is directional and far too many assumptions are made around the acceptance of accuracy.


We need to be aware of directional airflow in the sampling area or over the sampling rig and this airflow needs to be stabilised before we can assume that the result is correct.  The bell or impactor on a PM10 or PM2,5 rig can scavenge windblown dust and affect the dynamics of collection to the point where accuracy is affected in the same way as the cyclone rig, so we need to ask what we are sampling for and work within the limitation of the equipment we are using.


Finally, the cost of equipment and the labour needed to run sampling exercises, means that we try to minimise the number of samples that are taken as well as the position and we erroneously assume that these are representative.


* Sampling in one or two positions is not representative of conditions on a plant, surrounding a property, in a township or industrial area.
* Sampling on one or two days, a week or even a month is as inaccurate as a total guess when viewing permanent conditions.
* Most analysis methods demand samples of substance, more than the couple of micrograms collected in a PM10 or gravimetric dust sample with the result that inaccuracies of scale are being accepted.


To illustrate this, the City of Cape Town has about seven permanent monitoring stations around the Peninsula, which run at best erratically and often not at all and the results are accepted without question.


On mines, the dust levels come down all the time but silicosis cases increase – there is something wrong.  There are many cases out there with persons never having worked at a mine or lived near one.



Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.