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Hierarchy of Control

When looking to control exposure to hazardous substances, there are usually a number of different measures that can be implemented. Some of these measures will certainly be preferable to others, so it becomes prudent to list the controls in order of priority. This is the basis for the hierarchy of controls. Depending on the resource you use, there may be minor differences in the presentation of the idea, although they are all based on the same principles.

The hierarchy of control was developed by considering where the control can be applied, and which type of control is likely to be most effective. Control measures can be applied at either of the following three positions:

  • at the source of the contaminant

  • along the transmission path

  • at the worker.

Out of the three positions above, the best way to achieve control is by putting in controls at the source of contamination. It may be found controlling at source is not successful or practical, in this case then control measures should be applied along the transmission path, although it may be found that this is more difficult and there are less options available. Only when both of these options are determined to be ineffective or not achievable, should the primary control measure be based around the worker!

At Source

Examples of control measures that can be applied at the source of the contaminant are as follows:

  • Elimination – remove the source of contaminant.

  • Substitution – replace the source of contaminant with a less hazardous option.

  • Isolation – enclose the source of contaminant or the workers.

  • Modification – change the source of contaminant or the process involved.

  • Automation – carry out the process without the need for physical worker intervention.

  • Separation – place the source in a different place to the worker.

  • Local Exhaust Ventilation – use local exhaust ventilation systems to capture and contain the contaminant at source.

Along the Transmission Path

Examples of control measures that can be applied along the transmission path are as follows:

  • General ventilation – diluting the contaminant.

  • Increasing distance – by increasing the distance between the source of contaminant and the worker, more time will be available for dilution and dispersion.

  • Use of screens or barriers.

At the Worker

Examples of control measures that can be applied at the worker are as follows:

  • Administrative Controls – worker rotation, limiting exposure duration.

  • Personal Protective Equipment (PPE)– wearing something to prevent exposure such as gloves to prevent skin contact on the hands or a respiratory protective equipment (RPE) to control inhalation exposure. We have already written blogs on RPE.

It must be noted that there is a certain degree of subjectivity when applying these categories and some even fit into more than one; LEV for example is most effective when capturing the contaminant at source but if you are to observe a capture hood positioned to control welding fume, then perhaps it could be argued that is the along the transmission path?

Another example of a way to categorise controls measures are as follows:

  • Prevention

  • Engineering Controls

  • Procedural / Organisational Controls

  • Personal Protective Equipment

As discussed previously, the hierarchy of control can have minor differences in the presentation of the idea, although they are all based on the same principles. So, when you need to decide on what control measures to pick, be sure to start at the top of the hierarchy and prioritise these controls where possible. Continue working down through the hierarchy considering each measure as you go. Finally, the use of PPE can be justifiable in certain situations, such as cleaning, however, this should never be the first choice when controlling exposure to hazardous substances.

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At Blue Turtle Ltd, we provide a range of occupational hygiene monitoring services and can help you carry out your occupational health risk assessment. We can also help you to select the optimum control measures, better understand your local exhaust ventilation systems through LEV examination and testing services and carry out occupational exposure monitoring / personal exposure monitoring services to ensure you meet your legal obligations under the COSHH Regulations.

We help businesses of all types manage their workplace health hazards. Our experienced consultants can provide practical advice on how to achieve adequate control through process changes, improvements, or adopting/changing work practices to reduce the risk as low as reasonably practicable.

Whatever your Occupational Hygiene needs are, Blue Turtle Ltd is here to help your business protect your workforce and help you meet your legal obligations.

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