50   Definitions

In this Division:

atmospheric contaminant means:

(a)  a hazardous substance that occurs in the form of a fume, mist, gas, dust or vapour, or

(b)  an asphyxiant, or

(c)  nuisance dust,

to which persons may be exposed in the working environment.

inspirable dust means those airborne particles of dust that can be taken in through the nose or mouth during breathing.

respirable fibre means a fibrous particle with a diameter of less than 3 micrometres and a length of greater than 5 micrometres, with a length to width ratio of greater than 3:1, that can reach the deepest part of a lung.

safe oxygen level means a minimum oxygen content in air of 19.5% by volume under normal atmospheric pressure and a maximum oxygen content in air of 23.5% by volume under normal atmospheric pressure.

synthetic mineral fibre means any manufactured mineral fibre, including mineral woolrock (rockwool and slagwool), glasswool (including superfine glassfibre) and ceramic fibres.

synthetic mineral fibre dust means dust arising from a synthetic mineral fibre.

TWA (time-weighted average) means the average airborne concentration of a particular substance when calculated over a normal 8-hour working day for a 5-day working week.