What Are The "Principles Of Good Practice" Defined In The COSHH Regulations?

It is a requirement of the COSHH Regulations 2002, as amended in 2004 that the following 8 principles of good practice are used.


They must all be applied to obtain effective & reliable control. The principles overlap in their application. They are not rank ordered; the first is not more important than the last, although

there is a logic to their overall order of presentation.

  • Design & operate processes & activities to minimise emission, release & spread of substances hazardous to health.

  • Take into account all relevant routes of exposure - inhalation, skin absorption & ingestion - when developing control measures.

  • Control exposure by measures that are proportionate to the health risk.

  • Choose the most effective & reliable control options which minimise the escape & spread of substances hazardous to health.

  • Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment.

  • Check & review regularly all elements of control measures for their continuing effectiveness.

  • Inform & train all employees on the hazards & risks from the substances with which they work & the use of control measures developed to minimise the risks.

  • Ensure that the introduction of control measures does not increase the overall risk to health & safety.


The following guidance notes explain how to apply the principles in practice:


Principle (a). Design & operate processes & activities to minimise emission, release & spread of substances hazardous to health


It is more effective, & usually cheaper, to reduce the emission of a contaminant at source, rather than to develop ways of removing the contaminant from the workplace, once it has been released & dispersed. Sources of exposure should be reduced in number, size, emission or release rate, as much as possible. It is often not possible to obtain adequate & reliable control unless this is done. Both the processes & procedures need to be considered. To identify how people get exposed during work activities, it is essential to recognise the principal sources & how the contaminant is transferred within the workplace. It is easy to miss significant sources & causes of exposure.


Processes & activities can lead to the emission & release of contaminants. The way they do this & the scale of emission & release needs to be understood. Once this assessment is available, alterations can be developed to minimise emissions, release & spread of contaminants. It is best to do this at the design stage, but it may well be possible to make useful & relatively low-cost changes to existing processes. Identify & control the worst sources first. In practice, improvements to production & quality can often be useful additional benefits from such re-examinations.


People working near a process may be significantly exposed even though those directly involved are protected, for example by wearing PPE. In these circumstances, the most practical option may be to segregate the process. It may be the only viable way to protect those people not directly involved in the process or activity.


Once the number & size of sources have been minimised, consider reducing emissions by enclosure or other means. Where enclosures are used, they should be big enough & robust enough to cope with the processes, & the energy of contaminant emission or release involved. For airborne contaminants, properly designed exhaust ventilation applied to the enclosure may be needed to minimise leakage into the workplace.


Design work methods & organisation to minimise exposure. This normally requires clearly defined & described work methods. Organise the work to minimise the number of people exposed & the duration, frequency & level of exposure. An example would be when painting or coating a large object. If containment is not feasible, then natural ventilation may, with the right precautions, be relied on to disperse vapour. This would be done best at the end of a shift, in controlled circumstances & when fewer people will be present.


LEV is an important option for controlling exposure. LEV systems consist of an air mover (usually a fan), an air cleaner, ductwork, & inlet hoods or terminals. Many designers & much ventilation guidance concentrates on the air mover, air cleaner & ductwork. There is a strong tendency to treat the hood design as a minor matter often left to people onsite. Yet, if the airborne contaminant is not drawn into, or contained within, the LEV hood, exposure is likely to be poorly controlled. The hood size, shape, layout & airflow requirements should all be considered. This will define the design & airflow requirements for the other elements of the system (ductwork, fans, air cleaners etc). The hood should be designed to work effectively & cope with the way the process emits airborne contaminants. So, for instance, if the source is large or emits contaminant-laden air at high velocity, a small 'captor' type hood will not be effective. Apart from considering the process to be controlled, the LEV should be designed so that it is easy to use correctly. LEV hood design should be compatible with the system of work & the operator's requirements, such as lighting & heating. LEV hoods & the working methods required to get the best performance from them should be designed ergonomically.


In addition to identifying significant sources, it is essential to identify & consider all work groups that may be exposed. It is easy to underestimate the exposure of those engaged in non-routine activities such as work done by maintenance personnel/contractors. Also, be aware of, & have contingency plans for dealing with, failures of control & emergencies. In many instances it is possible to predict those parts of a production process that are likely to fail suddenly & modify or maintain them appropriately. Control measures, at the outset, should be designed for ease of use & maintenance. If they include working methods that are difficult to follow or involve hardware that is difficult to repair, the control measures will probably not be maintained or sustained. Their effectiveness will fall inevitably, & exposure will rise.



Principle (b). Take into account all relevant routes of exposure - inhalation, skin & ingestion - when developing control measures


Exposure can occur through:         

(a) inhalation;          

(b) skin;          

(c) ingestion.


The physical, chemical & infectious properties of a substance, in the circumstances of use, have a great bearing on which route of exposure, or combination of routes, is most important. If there is no exposure, there is no risk to health; but usage nearly always leads to some exposure. So, consider:

(a) the health effects that the substances can cause;

(b) the way the substances are used;

(c) the degree of exposure;

(d) how exposure occurs.


An adequate risk assessment considers all routes by which the substance might enter the body &, in the case of direct contact, how a substance might affect the skin.


In some cases, it might be immediately obvious that not all routes apply. For example, for people exposed to crystalline silica, the only relevant route of entry is by inhalation. Whereas, for work at room temperature with a low volatility substance, such as dimethyl formamide, the primary route of entry will be through the skin. Therefore:   

(a) identify all sources & routes of exposure;

(b) rank these routes in order of importance.


Where inhalation is the most relevant route, the main focus for control will be sources of emission to air. Where the main concern is ingestion or effects on, or as a result of penetration through the skin, then the main focus for control will be sources of contamination of surfaces or clothing & direct contamination of the skin.

Schedule 2A

Exposure assessments should identify &, if possible, grade/rank the contribution of all routes of exposure (inhalation, skin & ingestion) to total, exposure. In this way control effort is directed at the main sources & causes of exposure.


Prevent skin contact where possible if contamination may lead to skin absorption, ingestion or direct health effects on the skin. Regularly clean all surfaces that can become contaminated. The frequency of cleaning should be based on the rate at which the surfaces become contaminated & how often skin is likely to come into contact with them.

Gloves are often used to provide protection against skin contact with hazardous substances. However, transfer of contamination from the outside of protective gloves to the inside is common. Train users in the correct techniques for putting on & taking off their gloves. Ensure all surfaces, which need to be cleaned, are made of materials that are easily cleaned. For instance, use work surfaces, which are impermeable & smooth so that they are easy to wipe clean & easy to test by surface sampling, if necessary.


If the workroom is likely to become contaminated, & this contamination may contribute significantly to exposure, people should not increase their exposure by activities such as:

(a) eating;             

(b) drinking;          

(c) smoking;            

(d) using cosmetics in the workplace.


If the workroom is liable to be contaminated make sure people have clean areas to rest, eat & drink.