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Priority Assessment Score

Asbestos Knowledge Base


The HSE have introduced a prescribed method of carrying out risk assessments so that they provide a 'score' that allows the risks of one ACM to be compared to others and therefore prioritised. The higher the score the higher the risk. In addition, the HSE have indicated the need to add the Priority Assessment Score (PAS) to the Material Assessment Score (MAS) to provide a total Risk Assessment Score (RAS). This gives an overall score per ACM and further allows prioritisation within the management plan.

The are 4 components to the Priority assessment score;

  1. Occupant activity
  2. Likelihood of disturbance
  3. Human exposure potential
  4. Maintenance activity

Occupant activity

Activities carried out in an area will have an impact on the risk assessment. When you're carrying out a risk assessment, the main type of use of an area and the activities taking place within it should be taken into account. For example, a little used storeroom, or an attic, will rarely be accessed and so any asbestos present is unlikely to be disturbed. At the other end of the scale, in a warehouse lined with AIB panels, with frequent vehicular movements, the potential for disturbance of asbestos-containing materials is reasonably high and this would be a significant factor in the risk assessment. Maintenance activity is dealt with separately (see below).

The algorithm below is used to compute this component of the risk assessment score per ACM.

Main type of activity in area 0Rare disturbance activity (e.g. little used store room)
1Low disturbance activities (e.g. office type activity)
2Periodic disturbance (e.g. industrial or vehicular activity which may contact ACMs.)
3High levels of disturbance (e.g. Fire door with AIB sheet in constant)

Likelihood of Disturbance

The two factors that will determine the likelihood of disturbance are the extent or amount of the asbestos-containing material and its accessibility. For example, asbestos soffits are outdoors and generally inaccessible without the use of ladders or scaffolding, so they are unlikely to be disturbed. The asbestos cement roof of a hospital ward is also unlikely to be disturbed, but its extent would need to be taken into account in any risk assessment. However if the same ward had asbestos panels on the walls they would be much more likely to be disturbed by trolley/bed movements.

The algorithm below is used to compute this component of the risk assessment score per ACM.

1Large rooms or well-ventilated areas
2Rooms up to 100m²
3Confined spaces
Accessibility0Usually inaccessible or unlikely to be disturbed
1Occasionally likely to be disturbed
2Easily disturbed
3Routinely disturbed
Extent / amount0Small amounts or items (e.g. strings, gaskets)
1More than 10m² or 10m pipe run.
2Between 10 and 50 m² or 10 and 50m pipe run.
3More than 50m² or 50m pipe run.

Human Exposure Potential

The human exposure potential depends on three factors; the number of occupants of an area, the frequency of use of the area, and the average time each area is in use. For example, a factory boiler room is likely to be unoccupied, but may be visited daily for a few minutes. The potential for exposure is much less than say in an assembly shop lined with AIB paneling, with 30 workers, which is occupied daily for six hours.

The algorithm below is used to compute this component of the risk assessment score per ACM.

Number of occupants0None
3More than 10
Frequency of use of area0Infrequent
Average time area in use0Less than 1 hour
1Between 1 and 3 hours
2Between 3 and 6 hours
3More than 6 hours

Maintenance Activity

Maintenance trades such as plumbers and electricians are the group most at risk from accidental exposure to asbestos, so the work they carry out in an area should not be ignored. These activities may be as simple as changing a light bulb in an AIB ceiling or may be substantial such as replacing cabling, or installing new central heating systems. The frequency of maintenance activities also needs to be taken into account when carrying out a risk assessment. If light bulbs need to be changed as frequently as monthly, the risk will be greater than if they are only changed annually and this will have a bearing on the risk assessment conclusions and therefore on the management plan developed.

The algorithm below is used to compute this component of the risk assessment score per ACM.

Type of maintenance activity0Minor disturbance (e.g. possibility of contact when gaining access)
1Low disturbance (e.g. changing light bulbs in AIB ceiling)
2Medium disturbance (e.g. lifting one or two AIB ceiling tiles to access a valve)
3High levels of disturbance, (e.g. removing a number of AIB ceiling tiles to replace a valve or for recabling).
Frequency of maintenance activity0ACM unlikely to be disturbed for maintenance
1Less than or equal to 1 per year
2More than 1 per year
3More than 1 per month

The Risk Assessment

The risk assessment can only be carried out with a detailed knowledge of all the above factors. Although a surveyor may have some of the information which will contribute to the risk assessment and may be part of an assessment team the duty holder is required to make the risk assessment using the information given in the survey report and the detailed knowledge of activities carried on within the premises. If the surveyor is carrying out the work in-house, he/she may have the information required to enable the material assessment to be carried out, but they may require more detail from work colleagues for the risk assessment to be complete. The risk assessment will form the basis of the management plan.

Taking all these factors into account in a logical, consistent manner is difficult and it is suggested that again the use of an algorithm will help to provide a framework in which to produce risk assessments that have taken the factors into account in a consistent way. The use of algorithms is not infallible, but they do provide a transparency to the assessment process, so if discrepancies arise, it should be possible to track back through the assessment process to find the root of the error. It should be borne in mind though that they are tools and that further discussion/interpretation may be required before reaching conclusions.

The priority assessment algorithm considers relevant factors not covered in the material assessment (as outlined earlier). The number of factors relevant at any one site needs to be carefully considered, as the more factors that are included in an algorithm, the lower the influence of the most important risk factors becomes, and this may produce anomalies. For this reason the number of additional factors that are scored has been limited to four, the same number as factors in the material assessment.

There is no single set of factors that can be recommended that will apply equally to all types of premises. The four general headings used are suggested as a guide.

The Asbestos ToolKit CS™ software will enable the user to enter the various scores required and provide the priority assessment score (PAS) and Risk Assessment Score (RAS) into the database for onward reporting into the management system.