Clearing the air on dust control

TODAY’S dust monitoring technology provides greater versatility in sampling routines, enhanced precision in particulate analysis and less machine maintenance.

TODAY’S dust monitoring technology provides greater versatility in sampling routines, enhanced precision in particulate analysis and less machine maintenance. Felicity Sharp writes for Ecotech

Various kinds of air pollution can cause many harmful effects ranging from asthma to, in the most extreme cases, death. In the worst cases, air pollution disasters have claimed hundreds of lives.

In London between 1948 and 1956, heavy fogs and high air pollution were associated with the death of nearly 5,000 people more than expected for that time of year. During each incident, comparable conditions were present: limited air supplies as a result of low lying temperature inversions and faint winds combined with a heavy output of air pollution from many sources.

As such, industries which contribute to increased pollution levels are increasingly under pressure to clean up their act and keep below strict targets set by various government bodies. The mining industry is one such industry feeling the pressure. Ensuring businesses and residents are not unduly inconvenienced by pollutants is a major concern.

Regular environmental monitoring, where not mandated by regulation, is most certainly acknowledged as good practice. Not only does it create a baseline and a history of pollution levels but it can also provide evidence of reduced levels over time.

Particulates are commonly categorised according to their size and their ability to enter the lungs — the smaller the particulate, the deeper into the lungs it will penetrate. Total Suspended Particulates (TSP) refers to all size particles found in the air. The classification PM10 is particulate matter less than 10 microns in diameter, likewise PM2.5 is particulate matter with a diameter of less than 2.5 microns.

TSP and PM10 particulates come from a variety of sources, such as wind blown dust, sea salt spray, vegetation (i.e. pollens) and man made activities such as mining, quarrying and cement manufacturing. These particulates typically remain in the air from a few hours to several days.

The smaller PM2.5 particulates are most commonly from manufacturing/process industries that use combustion such as oil refineries, smelting and pulp mills. Residential burning (wood fires) and motor vehicle emissions are other major sources of particulate pollution. These particulates may remain in the air for weeks.

The concentration of particulates in the air varies greatly from location to location and depends not only on the source of particulates, but on existing meteorological conditions — such as temperature inversions — which affect concentration levels.

It has been established that the greatest health risk to human results from PM10 and PM2.5 particulates. It is quite common for PM2.5 particulates to enter the lungs and collect in the tiny air sacs, called “alveoli”, where oxygen enters the bloodstream. As a result, the particulates can cause breathing difficulties and sometimes permanent damage. Environmental Protection Agencies around the world place a great emphasis on monitoring these particulates.

Particulate monitoring solutions can provide data which can be used to distinguish between relatively harmless mineral dusts and soot (large particles which rarely enter the lungs), and more harmful finer particles, which have been proven to cause adverse health effects.

Particulates have been monitored since the early 1950s and the basic principle used by many monitors remains gravimetric analysis. Using a pump, a known volume of ambient air is drawn through a filter and the change in mass of the filter is measured with a micro-balance. Particulate concentration is then reported in micrograms per cubic metre of air sampled. Today, the well known measurement principle has been refined to facilitate improved versatility in sampling routines, more precise size selection of the various particulate fractions and decreased maintenance requirements.

The greatest changes in particulate sampling techniques have occurred due to the introduction of real time monitors. These units are able to continuously measure particulate concentrations in ambient air providing concentration averages in as little as a minute.

There is a wide selection of commercially available particulate monitors available on the market and selection depends on the application, frequency of data capture and whether or not real time information is mandated. It is important to speak with a specialist in the field to ensure that you find the right solution for your company.

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