Western Australian Current Regulations Western Australian Current Regulations (1) In this
regulation —
TWA concentration means the time weighted average
concentration of an atmospheric contaminant when calculated over a normal
8‑hour working period during a 5‑day working week.
(2) The exposure
standard for diesel particulates is a TWA concentration of 0.1 mg per
cubic metre of air (measured as sub‑micron elemental carbon).