1. Exposure Rating Exposure Rating Exposure Band Definition a) Very Low
< 0.1 x OEL
Exposures are negligible
b) Low
> <0.5 x OEL
Exposure are controlled well below OEL and are likely to remain so in accordance with standards
c) Medium
> 0.5 – 1 x OEL
Exposures are currently controlled below OEL to meet standards but control may be reliant on less robust measures such as personal protective equipment
d) High
> OEL
Exposure are not adequately controlled to meet standards and continuously/regularly exceed OEL
e) Very High
>> OEL
Exposures are excessive and will almost certainly result in health damage to persons exposed
The Exposure Rating should take into account control measures used to reduce exposure via all relevant routes, e.g. inhalation, skin contact, hearing, effects on musculo-skeletal system, etc. dependent on the hazard. It is easiest to assign a particular Exposure Rating category if measurement data are available, since that data can be compared directly against the OEL. Care must be taken to ensure that the data are representative of the current situation, and, if possible, data from normal and extreme conditions should be obtained. However, exposure measurement data are only one indicator of adequacy of control and are not always readily available. The Exposure Rating category should also consider the reliability of the existing control measures, including engineering methods, procedures and personal protective equipment, to reduce exposures. This is done by comparing the controls with standards of good practice using experience and judgment. Appendix 4 of the HRA yellow guide provides guidance on how to do this. Appendix 6 of the HRA yellow guide gives guidance on selection of OELs and other control standards with which to compare.
It is emphasised that the use of personal protective equipment (PPE) as the main measure of exposure control is not robust. In such situations, the type of PPE must be checked to ensure it is appropriate for the type and level of the hazard, and maintenance and training programmes must be confirmed. Where PPE is the main form of control, then the Exposure Rating will always be C as a minimum.

2. Control Chart
When the Hazard and Exposure Ratings are combined in a Controls Chart they provide a visual representation of the urgency of action required to strengthen controls.
The position on the chart represents a qualitative interpretation of the need for improved controls to ensure health risks are minimised. Risks can be reduced by moving the Exposure Rating from right to left by improving controls, and the Hazard Rating from bottom to top by substituting with less hazardous alternatives, where it is practicable to do so. The shading splits the need for action to improve controls in to three priorities - First, Second and Third, with a Fourth level not requiring immediate action. Please note that for those agents with the potential to cause irreversible health effects, permanent total disability or death, i.e. Hazard Ratings of 3, 4 or 5, the need for improved controls has been weighted to ensure they receive attention with appropriate priority, even where the Occupational Exposure Limit is not exceeded with the existing controls.