For the risk assessment, the employer estimates the level of dust corresponding to each work process and classifies them according to the following three levels:
a) First level: dust with a value of less than 100 fibres per litre ;
b) Second level: dust with a value greater than or equal to 100 fibres per litre and less than 6,000 fibres per litre;
c) Third level: dust with a value greater than or equal to 6,000 fibres per litre and less than 25,000 fibres per litre.