a. fibre: a particle longer than 5 µm, with a diameter smaller than or equal to 3 µm, and with a length to width ratio greater than or equal to 3:1; b. limit value: the maximum value of the average concentration of a chemical substance in an employee’s breathing zone over a fixed reference period of eight hours; c. chemical: any element, chemical compound or mixture thereof, whether it occurs naturally or is industrially produced or is used or released by any work operation, regardless of whether or not it is produced intentionally. This applies irrespective of whether the chemical is available on the market.
