Dust monitoring and control in the workplace

Dampening dust risks*

At its worst, exposure to airborne dust can lead to all kinds of occupational disease, from asthma to lung and nasal cancers. And at the very least, dusty environments are unpleasant and difficult to work in.

If you use dust producing processes the first step is to identify these processes, understand the substances involved and look at who is exposed.

There may only be a potential for exposure if not an actual problem, then back that up with measurements. It is only after the measurements have been taken can you make a reasonable judgement about what control measures are needed.

The dust itself might not be an issue, but there may be a toxic component to the dust so always check and use up-to-date safety data sheets. For example, a metal being grinded may have something like nickel or chromium in it, in which case you’ve got to control to a much greater degree.

Know the process

Dust exists in a range of sizes. The main fractions are “inhalable”, breathed into the nose or mouth; “thoracic”, which can penetrate the head airways and enter the airways of the lung; and “respirable”, which is most dangerous, and penetrates beyond the terminal bronchioles into the gas-exchange region of the lungs.

If you use dust producing processes such as in manufacturing, engineering and construction the first step is to identify these processes, understand the substances involved and look at who is exposed.

In some cases, just observing processes will indicate whether there is a problem. It is likely you have got a problem if there are clouds of dust everywhere, but conversely the size of dust we breath in is largely invisible to the naked eye, making some dust issues less obvious. Sampling is only going to tell you’ve got a problem, so it’s best to put controls in place and do the basics – such as some extraction – and then do some monitoring to ensure you’ve reduced it to acceptable levels.

In other cases, for something like a pharmaceutical or a metal, with a low exposure limit, it can be very difficult to assess visually, and you really do need to do some sampling first. Airborne dust is the real issue in health terms, not heavy dust lying around a machine, which makes it look dusty.

People also tend to focus on the wrong processes, perhaps the saw, where there is a lot of dust deposited on the floor. But they miss processes that are most likely to produce potentially high exposure, such as sanding or routing, which produce a much finer, inhalable dust.

So it’s about knowing your processes, knowing what you’re looking for and the types of substances you’re using, and then it’s about matching your choice of monitoring to that.

Choosing the method

Once you know the process, you have to select the relevant method then put in place controls to keep the safety of the workplace paramount. There are Australian standards such as AS2985 which should be used as the guiding basis for determining concentration levels and sampling procedures. OHS consultants are available to assist or even conduct procedures in your workplace to ensure safety and compliance.

Air pumps (such as Casella Apex2) are typically used for sampling  in the workplace and ensuring general compliance with safety.

Once you’ve decided what you’re looking for and found a method to work to, the method will state the volume of air to test and how long to run the pump for, and at what flow rate.

You need to be able to set an accurate flow rate and you need calibration equipment to do that. You’ve also got to do that before and after each sample, to check it hasn’t changed in the 8 hours you’ve been testing for.

Not having equipment calibrated properly is easy to do and can have serious consequences.

It is also important to look after and handle equipment properly. Filters must be stored appropriately – away from a humid environment where they could absorb moisture, which would change their weight, and handled with forceps or tweezers.

If you damage the filter or accidentally rip a bit off, that’s going to affect the weight you’re supposed to be measuring. With some types of sampling head the filter is in a cassette that goes in the head.

You then weigh the cassette, which stops you handling the filter and stops any dust collected being lost inside the walls of the head itself.

Taking blanks — which involves simply handling and returning a filter from the same batch to act as a control — is another key part of the sampling process that people sometimes miss, or ignore on cost grounds.

Using air pumps allows measurement against standards guidance, but there is another — and complementary — dust monitoring option, which offers real time measurement. Using real time monitoring device (such as Casella Microdust Pro) gives you an idea there and then if you’ve got a problem or not rather than waiting for a lab result, so you can make changes to your process or dust control measures, and do some new measurements.

With real time monitoring, you can leave the device in the area to log how dust levels vary through time, which provides useful information about exactly where the dust problem lies, at what point in the process, and where you need to focus control measures.

Control hierarchy

In controlling dusts, the usual risk control hierarchy applies:

• eliminate use

• use a safer form of the product, such as a paste rather than powder

• change the process to emit less dust

• enclose the process so that the dust does not escape or extract dust near the source using local exhaust ventilation

• have as few workers in harm’s way as possible

• provide personal protective equipment (PPE) such as a respirator

The hierarchy is about recognising you can do things at the front end to prevent exposure at other end. If you alter the process or use materials without a toxic component, or in a form that doesn’t generate exposure, it’s better than having to control the dust.

Always consult with qualified OHSE industry experts to ensure compliance and the safety of the workplace.

[*] Based on an article originally published by Casella Solutions for general information only.

 

                                         

CEL-712 Microdust Pro -Handheld for real time monitoring           Apex2 -Personal Air Sampling Pumps

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