substance The requirement is for a review of the assessment. This does not mean that the whole assessment process will have to be repeated at each review. The first purpose of review is to see if the existing assessment is still suitable and sufficient.  If it is, then you do not need to do any more. If it appears that the assessment is no longer valid, it does not mean that the whole assessment has to be revised.  Only those parts that do not reflect the new situation need amending. Whether or not there is any real change in the situation, there is an absolute requirement to review the situation on a regular basis. Without this, there is a danger that gradual change over a period of time goes unnoticed and the assessment becomes unsuitable and insufficient by default. Some substances are process generated, for example wood dust produced from sawing wood. Employers should regard a substance as hazardous to health if it is hazardous in the form in which it occurs in the work activity. You should find out if there are any health effects associated with working with the hazardous materials identified and look at how workers could be exposed, for example do you use a dry brush to sweep up dust? Use this information to evaluate risks to health and minimise exposure by taking sensible measures, such as using a vacuum cleaner instead of a brush, or keeping lids on containers. How do I carry out a