COSHH Essentials

COSHH Essentials is a tool developed by the UK Health and Safety Executive. It’s a “control banding” technique which was originally intended to help small companies, without access to expert help, determine what controls are needed to control exposure to the hazardous substances they use or handle.

It was originally published as a “hard copy” manual in 1999, an online version appearing a few years later. The hard copy is no longer available.

In essence COSHH Essentials is a mathematical modelling tool which estimates exposure. The user enters some basic information on the substance being used (“R phrases”, boiling point or “dustiness”  and the amount used). The tool uses these details to determine which “control approach” is appropriate and the user is directed to simple control sheets relevant to the risk and the type of process.

It is a very simple tool that can work in straightforward situations where a single substance or “preparation” is being handled. However, it has some very serious limitations.

The following slides provide a more detailed outline of the process and a couple of examples to show how it works in practice

The two examples used in the presentation illustrate some of the strengths and weaknesses of the approach.

In the first scenario, where a low hazard powder is being weighed and mixed with water to form a slurry the only significant risk is inhalation of airborne dust and the tool works quite well. The specified control – local exhaust ventilation – seems appropriate. The scenario is based on a real situation where I recommended installing an extracted booth, and one of the control sheets generated by the tool provides a suitable design.

However, I think the conclusions and guidance provided for the second example – cleaning rollers with solvent – illustrate some of the problems with COSHH Essentials. Here there are two significant risks – inhalation of solvent vapours and skin contact with the liquid solvent. The tool is particularly poor where the latter is an issue. It doesn’t attempt to assess skin exposure other than directing the user to personal protective equipment (PPE) wherever skin or eye hazards are flagged up by the R phrases. Use of PPE should always be the last resort. Preventative measures and engineering controls are always preferable and should be considered first. This applies to skin contact as well as inhalation risks. In fact, protective gloves are rarely as effective as the user perceives and their introduction can sometimes be counter productive due to this. So, for this scenario I would have looked at finding an alternative solution such as using an applicator that minimised contact. Gloves might still be needed, but as a backup rather than the primary control.

My second concern with the output from the model for the second scenario is that it recommends enclosure of the process. Personally, I think this is over cautious. I think that local exhaust ventilation (LEV) would be adequate here. Enclosure would require automation and also LEV and, although quite feasible, this approach would be relatively expensive and I wouldn’t consider it to be “reasonably practicable” where only a few litres of solvent are used per day. This problem occurs because the usage category “medium” is specified where litre quantities of a substance are used. There is likely to be a big difference in risk between using 4 or 5 litres of a substance and 500 litres – yet in both cases the user is directed to classifying the quantity used as “medium”. I think the category is too broad. With this particular scenario, it would be better to consider the quantity as “small”. The tool would then specify “engineering controls” – effectively LEV – as the appropriate control approach. This seems much more reasonable to me. However I think that a user is most likely to classify use as “medium”. In this case COSHH Essentials is over cautious. That’s better than underestimating the risk, but could lead to more expense than really necessary.

In both the scenarios only a single substance was being used for relatively short durations. Where highly toxic substances, such as carcinogens, are used, or the process is more complex, particularly where there is more than one material or where substances are generated during the process, the use of COSHH essentials is unlikely to be appropriate.


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